Effect of the Si-doped In_(0.49)Ga_(0.51)P barrier layer on the device performance of In_(0.4)Ga_(0.6)As MOSFETs grown on semi-insulating GaAs substrates

In0.4Ga0.6As channel metal-oxide-semiconductor field-effect transistors （MOSFETs） with and without an Si-doped In0.49Ga0.51P barrier layer grown on semi-insulating GaAs substrates have been investigated for the first time. Compared with the In0.4Ga0.6As MOSFETs without an In0.49Ga0.51P barrier layer, In0.4Ga0.6As MOSFETs with an In0.49Ga0.51P barrier layer show higher drive current, higher transconductance, lower gate leakage current, lower subthreshold swing, and higher effective channel mobility. These In0.4Ga0.6As MOSFETs （gate length 2 μm） with an In0.49Ga0.51P barrier layer exhibit a high drive current of 117 mA/mm, a high transconductance of 71.9 mS/mm, and a maximum effective channel mobility of 1266 cm2/（V·s）.

Fabrication and Characterization of 1700 V 4H-SiC Vertical Double-Implanted Metal-Oxide-Semiconductor Field-Effect Transistors

The fabrication and characterization of 1700 V 7 A 4H-SiC vertical double-implanted metal-oxide-semiconductor field-effect transistors （VDMOSFETs） are reported. The drift layer is 17μm in thickness with 5 × 10^15 cm^-3 n-type doping, and the channel length is 1μm. The MOSFETs show a peak mobility of 17cm2/V.s and a typical threshold voltage of 3 V. The active area of 0.028cm2 delivers a forward drain current of 7A at Vcs = 22 V and VDS= 15 V. The specific on-resistance （Ron,sv） is 18mΩ.cm2 at VGS= 22 V and the blocking voltage is 1975 V （IDS 〈 lOOnA） at VGS = 0 V.

The Impact of HC1 Precleaning and Sulfur Passivation on the Al2O3/Ge Interface in Ge Metal-Oxide-Semiconductor Capacitors

Surface treatment for Ge substrates using hydrogen chlorine cleaning and chemical passivation are investigated on AuTi/Al2O3/Ge metal-oxide-semiconductor capacitors.After hydrogen chlorine cleaning,a smooth Ge surface almost free from native oxide is demonstrated by atomic force microscopy and x-ray photoelectron spectroscopy observations.Passivation using a hydrogen chlorine solution is found to form a chlorine-terminated surface,while aqueous ammonium sulfide pretreatment results in a surface terminated by Ge-S bonding.Compared with chlorine-passivated samples,the sulfur-passivated ones show less frequency dispersion and better thermal stability based on capacitance-voltage characterizations.The samples with HCl pre-cleaning and (NH4 )2S passivation show less frequency dispersion than the HF pre-cleaning and (NH4)2S passivated ones.The surface treatment process using hydrogen chlorine cleaning followed by aqueous ammonium sulfide passivation demonstrates a promising way to improve gate dielectric/Ge interface quality.

The Microwave Characteristics of an In_(0.4)Ga_(0.6)As Metal-Oxide-Semiconductor Field-Effect Transistor with an In_(0.49)Ga_(0.51)P Interfacial Layer

A high microwave performance enhancement-mode(E-mode)In_(0.4)Ga_(0.6)As channel metal-oxide-semiconductor field-effect transistor(MOSFET)with a Si-doped In_(0.49)Ga0.51P interfacial layer is fabricated.A 0.8-μm-gate-length In_(0.4)Ga_(0.6)As MOSFET with a 5-nm Al_(2)O_(3) dielectric layer provides a current gain cutoff frequency of 16.7 GHz and a maximum oscillation frequency of 52 GHz.A semi-empirical small-signal-parameter extraction technique accounting for the low frequency anomaly of this MOSFET device is described,which is based on on-wafer S-parameter measurements.Excellent agreement between measured and simulated scattering parameters as well as the physically realistic circuit elements demonstrates the validity of this approach.

Charge trapping behavior and its origin in Al_2O_3/SiC MIS system

Charge trapping behavior and its origin in Al2O3/SiC MOS structure are investigated by analyzing the capacitance–voltage(C–V) hysteresis and the chemical composition of the interface. The C–V hysteresis is measured as a function of oxide thickness series for an Al2O3/SiC MIS capacitor. The distribution of the trapped charges, extracted from the C–V curves, is found to mainly follow a sheet charge model rather than a bulk charge model. Therefore, the electron injection phenomenon is evaluated by using linear fitting. It is found that most of the trapped charges are not distributed exactly at the interface but are located in the bulk of the Al2O3 layers, especially close to the border. Furthermore, there is no detectable oxide interface layer in the x-ray photoelectron spectroscope(XPS) and transmission electron microscope(TEM)measurements. In addition, Rutherford back scattering(RBS) analysis shows that the width of the Al2O3/SiC interface is less than 1 nm. It could be concluded that the charge trapping sites in Al2O3/SiC structure might mainly originate from the border traps in Al2O3 film rather than the interface traps in the interfacial transition layer.

Annealing temperature influence on the degree of inhomogeneity of the Schottky barrier in Ti/4H–SiC contacts

Tung＇s model was used to analyze anomalies observed in Ti/Si C Schottky contacts. The degree of the inhomogeneous Schottky barrier after annealing at different temperatures is characterized by the ‘T0anomaly＇ and the difference（△Φ）between the uniformly high barrier height（Φ0B） and the effective barrier height（Φeff B）. Those two parameters of Ti Schottky contacts on 4H–Si C were deduced from I–V measurements in the temperature range of 298 K–503 K. The increase in Schottky barrier（SB） height（ΦB） and decrease in the ideality factor（n） with an increase measurement temperature indicate the presence of an inhomogeneous SB. The degree of inhomogeneity of the Schottky barrier depends on the annealing temperature, and it is at its lowest for 500-°C thermal treatment. The degree of inhomogeneity of the SB could reveal effects of thermal treatments on Schottky contacts in other aspects.

High-mobility germanium p-MOSFETs by using HCl and(NH_4)_2S surface passivation

To achieve a high-quality high-κ/Ge interfaces for high hole mobility Ge p-MOSFET applications, a simple chemical cleaning and surface passivation scheme is introduced, and Ge p-MOSFETs with effective channel hole mobility up to 665 cm2/V.s are demonstrated on a Ge （111） substrate. Moreover, a physical model is proposed to explain the dipole layer formation at the metal-oxide-semiconductor （MOS） interface by analyzing the electrical characteristics of HCl- and （NH4）2S-passivated samples.

Solid Phase Reactions of Ni-GaAs Alloys for High Mobility Ⅲ-Ⅴ MOSFET Applications

The solid phase reactions of Ni with GaAs substrates are investigated.The experimental results reveal that the Ni-GaAs solid phase reaction forms a ternary phase of Ni2GaAs when annealing temperatures are in the range 250 300℃.As the annealing temperature increases to 400℃,the Ni2GaAs phase starts to decompose due to NiAs phase precipitation.Ni-GaAs alloys processed at 400℃ with a 3min annealing time demonstrate a sheet resistance of 30Ω/square after unreacted Ni removal in hot diluted-HCl solutions.Therefore,Ni-GaAs alloys formed by solid phase reaction could be promising metallic source/drain structures with significant low series resistance for high mobility Ⅲ-Ⅴ metal-oxide-semiconductor field effect transistor (MOSFET) applications.

A High Performance In_(0.7)Ga_(0.3)As MOSFET with an InP Barrier Layer for Radio-Frequency Application

We demonstrate a high performance implant-free n-type In_(0.7)Ga_(0.3)As channel MOSFET with a 4-nm InP barrier layer fabricated on a semi-insulating substrate employing a 10-nm Al_(2)O_(3) as gate dielectric.The maximum effective channel mobility is 1862 cm^(2)/V·s extracted by the split C–V method.Devices with 0.8μm gate length exhibit a peak extrinsic transconductance of 85 mS/mm and a drive current of more than 200 mA/mm.A short-circuit current gain cutoff frequency f_(T) of 24.5 GHz and a maximum oscillation frequency f_(max) of 54 GHz are achieved for the 0.8μm gate-length device.The research is helpful to obtain higher performance In_(0.7)Ga_(0.3)As MOSFETs for radio-frequency applications.

GaSb p-Channel Metal-Oxide-Semiconductor Field-Effect Transistors with Ni/Pt/Au Source/Drain Ohmic Contacts

GaSb is an attractive candidate for future high-performance Ⅲ-Ⅴ p-channel metal-oxide-semiconductor-field-effect-transistors(pMOSFETs)because of its high hole mobility.The effect of HCl based-chemical cleaning on removing the non-self limiting and instable native oxide layer of GaSb to obtain a clean and smooth surface has been studied.It is observed that the rms roughness of a GaSb surface is significantly reduced from 2.731 nm to 0.693 nm by using HCl:H_(2)O(1:3)solution.The Ni/Pt/Au ohmic contact exhibits an optimal specific contact resistivity of about 6.89×10^(-7)Ω·cm^(2) with a 60 s rapid thermal anneal(RTA)at 250℃.Based on the chemical cleaning and ohmic contact experimental results,inversion-channel enhancement GaSb pMOSFETs are demonstrated.For a 6μm gate length GaSb pMOSFET,a maximum drain current of about 4.0 mA/mm,a drain current on-off(ION/IOFF)ratio of>10^(3),and a subthreshold swing of~250 mV/decade are achieved.Combined with the split C-V method,a peak hole mobility of about 160 cm^(2)/V·s is obtained for a 24μm gate length GaSb pMOSFET.

Characterization of the effects of nitrogen and hydrogen passivation on SiO2/4H-SiC interface by low temperature conductance measurements

We investigate the effects of NO annealing and forming gas （FG） annealing on the electrical properties of a SiO2/SiC interface by low-temperature conductance measurements. With nitrogen passivation, the density of interface states （DIT） is significantly reduced in the entire energy range, and the shift of flatband voltage, AVFB, is effectively suppressed to less than 0.4 V. However, very fast states are observed after NO annealing and the response frequencies are higher than 1 MHz at room temperature. After additional FG annealing, the DIT and AVFB are further reduced. The values of the DIT decrease to less than 1011 cm-2 eV- 1 for the energy range of Ec - ET 〉/0.4 eV. It is suggested that the fast states in shallow energy levels originated from the N atoms accumulating at the interface by NO annealing. Though FG annealing has a limited effect on these shallow traps, hydrogen can terminate the residual Si and C dangling bonds corresponding to traps at deep energy levels and improve the interface quality further. It is indicated that NO annealing in conjunction with FG annealing will be a better post-oxidation process method for high performance SiC MOSFETs.

AlGaN/GaN high electron mobility transistor with Al_2O_3+BCB passivation

In this paper, Al2O3 ultrathin film used as the surface passivation layer for A1GaN/GaN high electron mobility transistor （HEMT） is deposited by thermal atomic layer deposition （ALD）, thereby avoiding plasma-induced damage and erosion to the surface. A comparison is made between the surface passivation in this paper and the conventional plasma enhanced chemical vapor deposition （PECVD） SiN passivation. A remarkable reduction of the gate leakage current and a significant increase in small signal radio frequency （RF） performance are achieved after applying Al2O3＋BCB passivation. For the Al2O3＋BCB passivated device with a 0.7μm gate, the value of fmax reaches up to 100 GHz, but it decreases to 40 GHz for SiN HEMT. The fmax/ft ratio （〉 4） is also improved after Al2O3＋BCB passivation. The capacitancevoltage （C-V） measurement demonstrates that Al2O3＋BCB HEMT shows quite less density of trap states （on the order of magnitude of 1010 cm-2） than that obtained at commonly studied SiN HEMT.

Fabrication of a novel RF switch device with high performance using In0.4Ga0.6As MOSFET technology

A novel radio frequency （RF） switch device has been successfully fabricated using InGaAs metal- oxide-semiconductor field-effect transistor （MOSFET） technology. The device showed drain saturation currents of 250 mA/mm, a maximum transconductance of 370 mS/ram, a turn-on resistance of 0.72 mx2.mm2 and a drain current on-off （Ionloll） ratio of 1 x 106. The maximum handling power of on-state of 533 mW/mm and off-state of 3667 mW/mm is obtained. The proposed In0.4Ga0.6As MOSFET RF switch showed an insertion loss of less than 1.8 dB and an isolation of better than 20 dB in the frequency range from 0.1 to 7.5 GHz. The lowest insertion loss and the highest isolation can reach 0.27 dB and more than 68 dB respectively. This study demonstrates that the InGaAs MOSFET technology has a great potential for RF switch application.

High-Performance In0.23Ga0.77As Channel MOSFETs with High Current Ratio Ion/Ioff Grown on Semi-insulating GaAs Substrates by MOCVD

We demonstrate high-performance In0.23 Ga0.77 As channel metal-oxide-semiconductor field-effect transistors （ MOS- FETs） with high on-current to off-current （Ion/Ioff） ratio grown on semi-insulating GaAs wafers by metal-organic chemical vapor deposition （MOCVD）. The 2μm channel-length devices exhibit a peak extrinsic transeonductance of 150 mS/mm and a drain current up to 500 mA/mm. The maximum effective mobility is 1680 cm2/Vs extracted by the split C-V method. Furthermore, the Ion/Ioff ratio is significantly improved from approximately 4.5 × 10^3 up to approximately 4.32 × 10^4 by controlling the etch thickness of In0.49Ga0.51P, The high drain current and high Ion/Ioff ratio of the In0.23Ga0.77As channel MOSFETs are achieved due to the high effective mobility and the low gate leakage current density.

Improved adhesion and interface ohmic contact on n-type 4H-SiC substrate by using Ni/Ti/Ni

The Ni/Ti/Ni multilayer ohmic contact properties on a 4H-SiC substrate and improved adhesion with the Ti/Au overlayer have been investigated. The best specific contact resistivity of 3.16 × 10^-5 Ω.cm^2 was obtained at 1050 ℃. Compared with Ni/SiC ohmic contact, the adhesion between Ni/Ti/Ni/SiC and the Ti/Au overlayer was greatly improved and the physical mechanism under this behavior was analyzed by using Raman spectroscopy and X-ray energy dispersive spectroscopy （EDS） measurement. It is shown that a Ti-carbide and Ni-silicide compound exist at the surface and there is no graphitic carbon at the surface of the Ni/Ti/Ni structure by Raman spectroscopy, while a large amount of graphitic carbon appears at the surface of the Ni/SiC structure, which results in its bad adhesion. Moreover, the interface of the Ni/Ti/Ni/SiC is improved compared to the interface of Ni/SiC.

Effect of ultrathin GeO_x interfacial layer formed by thermal oxidation on Al_2O_3 capped Ge

We propose a modified thermal oxidation method in which an Al2O3 capping layer is used as an oxygen blocking layer （OBL） to form an ultrathin GeOx interracial layer, and obtain a superior Al2O3/GeOx/Ge gate stack. The GeOx interfacial layer is formed in oxidation reaction by oxygen passing through the Al2O3 OBL, in which theAl2O3 layer could restrain the oxygen diffusion and suppress the GeO desorption during thermal treatment. The thickness of the GeOx interfacial layer would dramatically decrease as the thickness of Al2O3 OBL increases, which is beneficial to achieving an ultrathin GeOx interfacial layer to satisfy the demand for small equivalent oxide thickness （EOT）. In addition, the thickness of the GeOx interfacial layer has little influence on the passivation effect of the Al2O3/Ge interface. Ge （100） p-channel metal- oxide-semiconductor field-effect transistors （pMOSFETs） using the Al2O3/GeOx/Ge gate stacks exhibit excellent electrical characteristics; that is, a drain current on-off （Ionloft） ratio of above 1 104, a subthreshold slope of - 120 mV/dec, and a peak hole mobility of 265 cm2/V.s are achieved.

High-Quality Single Crystalline Ge(111)Growth on Si(111)Substrates by Solid Phase Epitaxy

Heterogeneous integration of crystalline Ge layers on cleaned and H-terminated Si(111)substrates are demonstrated by employing a combination of e-beam evaporation and solid phase epitaxy techniques.High-quality single crystalline Ge(111)layers on Si(111)substrates with a smooth Ge surface and an abrupt interface between Ge and Si are obtained.An XRD rocking curve scan of the Ge(111)diffraction peak shovs a FWHM of only 260 arcsec for a 50-nm-thick Ge layer annealed at 600℃with a ramp-up rate of 20℃/s and a holding time of 1 min.The AFM images exhibit that the rms surface roughness of all the crystalline Ge layers are less than 2.1 nm.

The effect of nitridation and sulfur passivation for In0.53Ga0.47As surfaces on their Al/Al2O3/InGaAs MOS capacitors properties

The impact of nitridation and sulfur passivation for Ino.s3Gao.47As surfaces on the A1/A1203/InGaAs MOS capacitors properties was investigated by comparing the characteristics of frequency dispersion and hysteresis, calculating the Dit and ANbt values, and analyzing the interface traps and the leakage current. The results showed that both of the methods could form a passivation-layer on the InGaAs surface. The samples treated by N2 plasma could obtain good interface properties with the smallest frequency dispersion in the accumulation region, and the best hysteresis characteristics and good I-V properties were presented. Also the samples with （NH4）ESx treatment showed the smallest frequency dispersion near the flat-band region and a minimum Dit value of 2.6 x10^11 cm-2 eV-1.

MIM capacitors with various Al_2O_3 thicknesses for GaAs RFIC application

The impact of various thicknesses of Al2O3 metal-insulator-metal （MIM） capacitors on direct current and radio frequency （RF） characteristics is investigated. For 20 nm Al2O3, the fabricated capacitor exhibits a high capacitance density of 3850 pF/mm2 and acceptable voltage coefficients of capacitance of 681 ppm/V2 at 1 MHz. An outstanding VCC-a of 74 ppm/V2 at 1 MHz, resonance frequency of 8.2 GHz and Q factor of 41 at 2 GHz are obtained by 100 nm Al2O3 MIM capacitors. High-performance MIM capacitors using GaAs process and atomic layer deposition Al2O3 could be very promising candidates for GaAs RFIC applications.