A compact drain current including the variation of barrier heights and carrier quantization in ultrathin-body and double-gate Schottky barrier MOSFETs （UTBDG SBFETs） is developed. In this model, Schrodinger＇s equat...A compact drain current including the variation of barrier heights and carrier quantization in ultrathin-body and double-gate Schottky barrier MOSFETs （UTBDG SBFETs） is developed. In this model, Schrodinger＇s equation is solved using the triangular potential well approximation. The carrier density thus obtained is included in the space charge density to obtain quantum carrier confinement effects in the modeling of thin-body devices. Due to the quantum effects, the first subband is higher than the conduction band edge, which is equivalent to the band gap widening. Thus, the barrier heights at the source and drain increase and the carrier concentration decreases as the drain current decreases. The drawback of the existing models,which cannot present an accurate prediction of the drain current because they mainly consider the effects of Schottky barrier lowering （SBL） due to image forces,is eliminated. Our research results suggest that for small nonnegative Schottky barrier （SB） heights,even for zero barrier height, the tunneling current also plays a role in the total on-state currents. Verification of the present model was carried out by the device numerical simulator-Silvaco and showed good agreement.展开更多
The formation of low-resistance Ohmic contacts in Ga_(2)O_(3) is crucial for high-performance electronic devices. Conventionally, a titanium/gold(Ti/Au) electrode is rapidly annealed to achieve Ohmic contacts, resulti...The formation of low-resistance Ohmic contacts in Ga_(2)O_(3) is crucial for high-performance electronic devices. Conventionally, a titanium/gold(Ti/Au) electrode is rapidly annealed to achieve Ohmic contacts, resulting in mutual diffusion of atoms at the interface. However, the specific role of diffusing elements in Ohmic contact formation remains unclear.In this work, we investigate the contribution of oxygen atom diffusion to the formation of Ohmic contacts in Ga_(2)O_(3). We prepare a Ti/Au electrode on a single crystal substrate and conduct a series of electrical and structural characterizations.Using density functional theory, we construct a model of the interface and calculate the charge density, partial density of states, planar electrostatic potential energy, and I–V characteristics. Our results demonstrate that the oxygen atom diffusion effectively reduces the interface barrier, leading to low-resistance Ohmic contacts in Ga_(2)O_(3). These findings provide valuable insights into the underlying mechanisms of Ohmic contact formation and highlight the importance of considering the oxygen atom diffusion in the design of Ga_(2)O_(3)-based electronic devices.展开更多
Periodic solitons are studied in dispersion decreasing fibers with a cosine profile. The variable-coefficient nonlinear Schrrdinger equation, which can be used to describe the propagation of solitons, is investigated ...Periodic solitons are studied in dispersion decreasing fibers with a cosine profile. The variable-coefficient nonlinear Schrrdinger equation, which can be used to describe the propagation of solitons, is investigated analytically. Analytic soli- ton solutions for this equation are derived with the Hirota＇s bilinear method. Using the soliton solutions, we obtain periodic solitons, and analyze the soliton characteristics. Influences of physical parameters on periodic solitons are discussed. The presented results can be used in optical communication systems and fiber lasers.展开更多
In order to reduce deep level defects, the theory and process design of 4H-SiC homoepitaxial layer implanted by carbon ion are studied. With the Monte Carlo simulator TRIM, the ion implantation range, location of peak...In order to reduce deep level defects, the theory and process design of 4H-SiC homoepitaxial layer implanted by carbon ion are studied. With the Monte Carlo simulator TRIM, the ion implantation range, location of peak concentration and longitudinal straggling of carbon are calculated. The process for improving deep energy level in undoped 4H-SiC homoepitaxial layer by three times carbon ion-implantation is proposed, including implantation energy, dose, the SiO2 resist mask, annealing temperature, annealing time and annealing protection. The deep energy level in 4H-SiC material can be significantly improved by implantation of carbon atoms into a shallow surface layer. The damage of crystal lattice can be repaired well, and the carbon ions are effectively activated after 1 600 ℃ annealing, meanwhile, deep level defects are decreased.展开更多
We study a series of（HfO2）x（Al2O3）1-x /4H-SiC MOS capacitors. It is shown that the conduction band offset of HfO2 is 0.5 e V and the conduction band offset of Hf AlO is 1.11–1.72 e V. The conduction band offsets...We study a series of（HfO2）x（Al2O3）1-x /4H-SiC MOS capacitors. It is shown that the conduction band offset of HfO2 is 0.5 e V and the conduction band offset of Hf AlO is 1.11–1.72 e V. The conduction band offsets of（Hf O2）x（Al2O3）1-x are increased with the increase of the Al composition, and the（HfO2）x（Al2O3）1-x offer acceptable barrier heights（〉 1 e V）for both electrons and holes. With a higher conduction band offset,（Hf O2）x（Al2O3）1-x/4H-SiC MOS capacitors result in a ～ 3 orders of magnitude lower gate leakage current at an effective electric field of 15 MV/cm and roughly the same effective breakdown field of ～ 25 MV/cm compared to HfO2. Considering the tradeoff among the band gap, the band offset, and the dielectric constant, we conclude that the optimum Al2O3 concentration is about 30% for an alternative gate dielectric in 4H-Si C power MOS-based transistors.展开更多
First, electronic structures of perfect wurtzite 4H-SiC were calculated by using first-principle ultra-soft pseudopotential approach of the plane wave based on the density functional theory; and the structure changes,...First, electronic structures of perfect wurtzite 4H-SiC were calculated by using first-principle ultra-soft pseudopotential approach of the plane wave based on the density functional theory; and the structure changes, band structures, and density of states were studied. Then the defect energy level of carbon vacancy in band gap was examined by substituting the carbon in 4H-SiC with carbon vacancy. The calculated results indicate the new defect energy level generated by the carbon vacancy, and its location in the band gap in 4H-SiC, which has the character of deep acceptor. A proper explanation for green luminescence in 4H-SiC is given according to the calculated results which are in good agreement with our measurement results.展开更多
In this paper, 1.2 kV, 3.3 kV, and 5.0 kV class 4H-SiC power Schottky barrier diodes （SBDs） are fabricated with three N-type drift layer thickness values of 10 μm, 30μm, and 50 μm, respectively. The avalanche bre...In this paper, 1.2 kV, 3.3 kV, and 5.0 kV class 4H-SiC power Schottky barrier diodes （SBDs） are fabricated with three N-type drift layer thickness values of 10 μm, 30μm, and 50 μm, respectively. The avalanche breakdown capabilities, static and transient characteristics of the fabricated devices are measured in detail and compared with the theoretical pre- dictions. It is found that the experimental results match well with the theoretical calculation results and are very close to the 4H-SiC theoretical limit line. The best achieved breakdown voltages （BVs） of the diodes on the 10 p.m, 30 m, and 50 -tm epilayers are 1400 V, 3320 V, and 5200 V, respectively. Differential specific-on resistances （Ron-sp） are 2.1 m--cm2, 7.34 mO. cm2, and 30.3 m-. cm2, respectively.展开更多
This paper investigates the current-voltage （I-V） characteristics of Al/Ti/4H-SiC Schottky barrier diodes （SBDs） in the temperature range of 77 K-500 K, which shows that Al/Ti/4H SiC SBDs have good rectifying beha...This paper investigates the current-voltage （I-V） characteristics of Al/Ti/4H-SiC Schottky barrier diodes （SBDs） in the temperature range of 77 K-500 K, which shows that Al/Ti/4H SiC SBDs have good rectifying behaviour. An abnormal behaviour, in which the zero bias barrier height decreases while the ideality factor increases with decreasing temperature （T）, has been successfully interpreted by using thermionic emission theory with Gaussian distribution of the barrier heights due to the inhomogeneous barrier height at the A1/Ti/4H-SiC interface. The effective Richardson constant A＊ = 154 A/cm2 . K2 is determined by means of a modified Richardson plot In（I0/T2） - （qσ）2/2（κT）2 versus q/kT, which is very close to the theoretical value 146 A/cm2 · K2.展开更多
文摘A compact drain current including the variation of barrier heights and carrier quantization in ultrathin-body and double-gate Schottky barrier MOSFETs （UTBDG SBFETs） is developed. In this model, Schrodinger＇s equation is solved using the triangular potential well approximation. The carrier density thus obtained is included in the space charge density to obtain quantum carrier confinement effects in the modeling of thin-body devices. Due to the quantum effects, the first subband is higher than the conduction band edge, which is equivalent to the band gap widening. Thus, the barrier heights at the source and drain increase and the carrier concentration decreases as the drain current decreases. The drawback of the existing models,which cannot present an accurate prediction of the drain current because they mainly consider the effects of Schottky barrier lowering （SBL） due to image forces,is eliminated. Our research results suggest that for small nonnegative Schottky barrier （SB） heights,even for zero barrier height, the tunneling current also plays a role in the total on-state currents. Verification of the present model was carried out by the device numerical simulator-Silvaco and showed good agreement.
基金Projects supported by the National Natural Science Foundation of China (Grant Nos.61874084,61974119,and U21A20501)。
文摘The formation of low-resistance Ohmic contacts in Ga_(2)O_(3) is crucial for high-performance electronic devices. Conventionally, a titanium/gold(Ti/Au) electrode is rapidly annealed to achieve Ohmic contacts, resulting in mutual diffusion of atoms at the interface. However, the specific role of diffusing elements in Ohmic contact formation remains unclear.In this work, we investigate the contribution of oxygen atom diffusion to the formation of Ohmic contacts in Ga_(2)O_(3). We prepare a Ti/Au electrode on a single crystal substrate and conduct a series of electrical and structural characterizations.Using density functional theory, we construct a model of the interface and calculate the charge density, partial density of states, planar electrostatic potential energy, and I–V characteristics. Our results demonstrate that the oxygen atom diffusion effectively reduces the interface barrier, leading to low-resistance Ohmic contacts in Ga_(2)O_(3). These findings provide valuable insights into the underlying mechanisms of Ohmic contact formation and highlight the importance of considering the oxygen atom diffusion in the design of Ga_(2)O_(3)-based electronic devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61205064,51272202,and 61234006)the Visiting Scholar Funds of the Key Laboratory of Optoelectronic Technology and Systems of Chongqing University(Grant No.0902011812401 5)
文摘Periodic solitons are studied in dispersion decreasing fibers with a cosine profile. The variable-coefficient nonlinear Schrrdinger equation, which can be used to describe the propagation of solitons, is investigated analytically. Analytic soli- ton solutions for this equation are derived with the Hirota＇s bilinear method. Using the soliton solutions, we obtain periodic solitons, and analyze the soliton characteristics. Influences of physical parameters on periodic solitons are discussed. The presented results can be used in optical communication systems and fiber lasers.
基金Supported by the National Natural Science Foundation of China (No. 61006008)Xi'an Applied Materials Innovation Fund (No. XA-AM-200607)
文摘In order to reduce deep level defects, the theory and process design of 4H-SiC homoepitaxial layer implanted by carbon ion are studied. With the Monte Carlo simulator TRIM, the ion implantation range, location of peak concentration and longitudinal straggling of carbon are calculated. The process for improving deep energy level in undoped 4H-SiC homoepitaxial layer by three times carbon ion-implantation is proposed, including implantation energy, dose, the SiO2 resist mask, annealing temperature, annealing time and annealing protection. The deep energy level in 4H-SiC material can be significantly improved by implantation of carbon atoms into a shallow surface layer. The damage of crystal lattice can be repaired well, and the carbon ions are effectively activated after 1 600 ℃ annealing, meanwhile, deep level defects are decreased.
基金supported by the National Natural Science Foundation of China(Grant Nos.51272202 and 61234006)the Science Project of State Grid,China(Grant No.SGRI-WD-71-14-004)
文摘We study a series of（HfO2）x（Al2O3）1-x /4H-SiC MOS capacitors. It is shown that the conduction band offset of HfO2 is 0.5 e V and the conduction band offset of Hf AlO is 1.11–1.72 e V. The conduction band offsets of（Hf O2）x（Al2O3）1-x are increased with the increase of the Al composition, and the（HfO2）x（Al2O3）1-x offer acceptable barrier heights（〉 1 e V）for both electrons and holes. With a higher conduction band offset,（Hf O2）x（Al2O3）1-x/4H-SiC MOS capacitors result in a ～ 3 orders of magnitude lower gate leakage current at an effective electric field of 15 MV/cm and roughly the same effective breakdown field of ～ 25 MV/cm compared to HfO2. Considering the tradeoff among the band gap, the band offset, and the dielectric constant, we conclude that the optimum Al2O3 concentration is about 30% for an alternative gate dielectric in 4H-Si C power MOS-based transistors.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60876061)the Fundamental Research Funds for the Central Universities
文摘First, electronic structures of perfect wurtzite 4H-SiC were calculated by using first-principle ultra-soft pseudopotential approach of the plane wave based on the density functional theory; and the structure changes, band structures, and density of states were studied. Then the defect energy level of carbon vacancy in band gap was examined by substituting the carbon in 4H-SiC with carbon vacancy. The calculated results indicate the new defect energy level generated by the carbon vacancy, and its location in the band gap in 4H-SiC, which has the character of deep acceptor. A proper explanation for green luminescence in 4H-SiC is given according to the calculated results which are in good agreement with our measurement results.
基金supported by the National Natural Science Foundation of China(Grant Nos.61404098,61176070,and 61274079)the Doctoral Fund of Ministry of Education of China(Grant Nos.20110203110010 and 20130203120017)+1 种基金the National Key Basic Research Program of China(Grant No.2015CB759600)the Key Specific Projects of Ministry of Education of China(Grant No.625010101)
文摘In this paper, 1.2 kV, 3.3 kV, and 5.0 kV class 4H-SiC power Schottky barrier diodes （SBDs） are fabricated with three N-type drift layer thickness values of 10 μm, 30μm, and 50 μm, respectively. The avalanche breakdown capabilities, static and transient characteristics of the fabricated devices are measured in detail and compared with the theoretical pre- dictions. It is found that the experimental results match well with the theoretical calculation results and are very close to the 4H-SiC theoretical limit line. The best achieved breakdown voltages （BVs） of the diodes on the 10 p.m, 30 m, and 50 -tm epilayers are 1400 V, 3320 V, and 5200 V, respectively. Differential specific-on resistances （Ron-sp） are 2.1 m--cm2, 7.34 mO. cm2, and 30.3 m-. cm2, respectively.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60876061)the Key Laboratory Science Foundation (Grant No. 20090C1403)
文摘This paper investigates the current-voltage （I-V） characteristics of Al/Ti/4H-SiC Schottky barrier diodes （SBDs） in the temperature range of 77 K-500 K, which shows that Al/Ti/4H SiC SBDs have good rectifying behaviour. An abnormal behaviour, in which the zero bias barrier height decreases while the ideality factor increases with decreasing temperature （T）, has been successfully interpreted by using thermionic emission theory with Gaussian distribution of the barrier heights due to the inhomogeneous barrier height at the A1/Ti/4H-SiC interface. The effective Richardson constant A＊ = 154 A/cm2 . K2 is determined by means of a modified Richardson plot In（I0/T2） - （qσ）2/2（κT）2 versus q/kT, which is very close to the theoretical value 146 A/cm2 · K2.
