Review of gallium oxide based field-effect transistors and Schottky barrier diodes

Gallium oxide(Ga_2O_3), a typical ultra wide bandgap semiconductor, with a bandgap of ~4.9 e V, critical breakdown field of 8 MV/cm, and Baliga's figure of merit of 3444, is promising to be used in high-power and high-voltage devices.Recently, a keen interest in employing Ga_2O_3 in power devices has been aroused. Many researches have verified that Ga_2O_3 is an ideal candidate for fabricating power devices. In this review, we summarized the recent progress of field-effect transistors(FETs) and Schottky barrier diodes(SBDs) based on Ga_2O_3, which may provide a guideline for Ga_2O_3 to be preferably used in power devices fabrication.

High frequency doubling efficiency THz GaAs Schottky barrier diode based on inverted trapezoidal epitaxial cross-section structure

A high-performance terahertz Schottky barrier diode(SBD)with an inverted trapezoidal epitaxial cross-sectional structure featuring high varactor characteristics and reverse breakdown characteristics is reported in this paper.Inductively coupled plasma dry etching and dissolution wet etching are used to define the profile of the epitaxial layer,by which the voltage-dependent variation trend of the thickness of the metal-semiconductor contact depletion layer is modified.The simulation of the inverted trapezoidal epitaxial cross-section SBD is also conducted to explain the physical mechanism of the electric field and space charge region area.Compared with the normal structure,the grading coefficient M increases from 0.47 to 0.52,and the capacitance modulation ratio(C^(max)/C_(min))increases from 6.70 to 7.61.The inverted trapezoidal epitaxial cross-section structure is a promising approach to improve the variable-capacity ratio by eliminating the accumulation of charge at the Schottky electrode edge.A 190 GHz frequency doubler based on the inverted trapezoidal epitaxial cross-section SBD also shows a doubling efficiency of 35%compared to that 30%of a normal SBD.

Modeling,simulations,and optimizations of gallium oxide on gallium-nitride Schottky barrier diodes

With technology computer-aided design(TCAD)simulation software,we design a new structure of gallium oxide on gallium-nitride Schottky barrier diode(SBD).The parameters of gallium oxide are defined as new material parameters in the material library,and the SBD turn-on and breakdown behavior are simulated.The simulation results reveal that this new structure has a larger turn-on current than Ga2O3 SBD and a larger breakdown voltage than Ga N SBD.Also,to solve the lattice mismatch problem in the real epitaxy,we add a Zn O layer as a transition layer.The simulations show that the device still has good properties after adding this layer.

Self-assembled patches in PtSi/n-Si(111)diodes

Using the effect of the temperature on the capacitance–voltage（C–V）and conductance–voltage（G/ω–V）characteristics of PtSi/n-Si（111）Schottky diodes the profile of apparent doping concentrationthe potential difference between the Fermi energy level and the bottom of the conduction bandapparent barrier heightseries resistanceand the interface state density Nss have been investigated.From the temperature dependence of（C–V）it was found that these parameters are non-uniformly changed with increasing temperature in a wide temperature range of 79–360 K.The voltage and temperature dependences of apparent carrier distribution we attributed to the existence of self-assembled patches similar the quantum wells,which formed due to the process of Pt Si formation on semiconductor and the presence of hexagonal voids of Si（111）.

Efficient thermal dissipation in wafer-scale heterogeneous integration of single-crystalline𝛽β-Ga_(2)O_(3)thin film on SiC

The semiconductor,β-Ga_(2)O_(3)is attractive for applications in high power electronic devices with low conduction loss due to its ultra-wide bandgap(∼4.9 eV)and large Baliga’s figure of merit.However,the thermal conductivity of𝛽β-Ga_(2)O_(3)is much lower than that of other wide/ultra-wide bandgap semiconductors,such as SiC and GaN,which results in the deterioration of𝛽β-Ga_(2)O_(3)-based device performance and reliability due to self-heating.To overcome this problem,a scalable thermal management strategy was proposed by heterogeneously integrating wafer-scale single-crystalline𝛽β-Ga_(2)O_(3)thin films on a highly thermally conductive SiC substrate.Characterization of the transferred𝛽β-Ga_(2)O_(3)thin film indicated a uniform thickness to within±2.01%,a smooth surface with a roughness of 0.2 nm,and good crystalline quality with an X-ray rocking curves(XRC)full width at half maximum of 80 arcsec.Transient thermoreflectance measurements were employed to investigate the thermal properties.The thermal performance of the fabricated𝛽β-Ga_(2)O_(3)/SiC heterostructure was effectively improved in comparison with that of the𝛽β-Ga_(2)O_(3)bulk wafer,and the effective thermal boundary resistance could be further reduced to 7.5 m 2 K/GW by a post-annealing process.Schottky barrier diodes(SBDs)were fabricated on both a𝛽β-Ga_(2)O_(3)/SiC heterostructured material and a𝛽β-Ga_(2)O_(3)bulk wafer.Infrared thermal imaging revealed the temperature increase of the SBDs on𝛽β-Ga_(2)O_(3)/SiC to be one quarter that on the𝛽β-Ga_(2)O_(3)bulk wafer with the same applied power,which suggests that the combination of the𝛽-Ga_(2)O_(3)thin film and SiC substrate with high thermal conductivity promotes heat dissipation in𝛽β-Ga_(2)O_(3)-based devices.