Han Yin Liu

Enhanced AlGaN/GaN MOS-HEMT Performance by Using Hydrogen Peroxide Oxidation Technique

This paper investigates enhanced device characteristics of AlGaN/GaN metal-oxide-semiconductor high electron mobility transistor (HEMT) (MOS-HEMT) fabricated by using hydrogen peroxide (H2O2) oxidation technique which demonstrates the advantages of simplicity and cost effectiveness. A 13-nm-thick Al2O3 oxide was grown upon the surface of AlGaN barrier layer and served as the gate dielectric layer and the surface passivation layer at the same time to effectively decrease gate leakage current and prevent RF current collapse, which are the critical issues of nitride HEMTs. Enhanced device performances of dc, RF, power, and reliability of the present MOS-HEMT are comprehensively investigated as compared with a conventional Schottky-gate HEMT.

Novel Oxide-Passivated AlGaN/GaN HEMT by Using Hydrogen Peroxide Treatment

This brief reports, for the first time, an oxide passivated AlGaN/GaN high electron mobility transistor by using the hydrogen peroxide (H2O2) treatment. Characterizations by using electron spectroscopy for chemical analysis and transmission electron microscopy have been performed to verify the formation of surface oxide on the AlGaN barrier layer. The present design has demonstrated superior improvements of 41% in the maximum drain/source current density IDS,max; 39% in the drain/source saturation current density at zero gate bias IDSSO, 47% in the maximum extrinsic transconductance gm,max, 53.2% in the two-terminal gate/drain breakdown voltage BVGD 36% in the cutoff frequency fT, and 20% in the maximum oscillation frequency fmax, as compared with an unpassivated conventional device.

A Simple Gate-Dielectric Fabrication Process for AlGaN/GaN Metal–Oxide–Semiconductor High-Electron-Mobility Transistors

This letter reports a simple processing method for fabricating metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) by using hydrogen peroxide (H₂O₂) oxidation technique. Aluminum oxide (AlO_x) was formed on the surface of the AlGaN barrier as the gate dielectric of the MOS-gate structure. By using the capacitance-voltage measurement, the dielectric constant (κ) of AlO_x was determined to be 9.2. The present MOS-HEMT has demonstrated enhanced saturation drain current density at V_GS = 0 V (I_DSS0) of 552.3 mA/mm, maximum extrinsic transconductance (g_{m, max}) of 136 mS/mm, wide gate voltage swing of 2.9 V, and two-terminal gate-drain breakdown/turn-on voltages (BV_GD/V_on) of -132.2/1.82 V.

Investigations of AlGaN/AlN/GaN MOS-HEMTs on Si Substrate by Ozone Water Oxidation Method

Al_0.3Ga_0.7N/AlN/GaN metal-oxide-semiconductor high electron mobility transistors (HEMTs) grown on Si substrates by using ozone water oxidation method are investigated. Superior improvements of 52.2% in two-terminal gate-drain breakdown voltage (BV_GD), 30.3% in drain-source current density (I_DS) at V_GS = 0 V (I_DSS0), 43.6% in maximum I_DS (I_DS,max), 34.7% in maximum extrinsic transconductance (<i>gm</i>,max), and 52.7%/34.3% in unity-gain cutoff/maximum oscillation frequency (<i>fT</i>/<i>f</i>_max) are achieved as compared with a reference Schottky-gated HEMT. Thermal stability is studied by conducting temperature-dependent characterizations of devices at ambient temperatures of 300-550 K. Time-dependent electrical reliability analyses for the devices stressed in off-state (V_GS = -20 V and V_DS = 0 V) for 0-60 h and on-state (V_GS = 2 V and V_DS = 20 V) for 0-20 h are also made to physically investigate the dominant degradation mechanisms. Excellent reliability and thermal stability at 300-550 K are achieved by the present design.

A Simple Passivation Technique for AlGaN/GaN Ultraviolet Schottky Barrier Photodetector

This letter demonstrates and investigates AlGaN/GaN ultraviolet photodetector (UV-PD) with a simple passivation process. The hydrogen peroxide (H₂O₂) oxidation technique is adopted to complete the passivation. The results of chemical analysis suggest that the Al and Ga dangling bonds react with the oxygen atoms. This passivation process effectively reduces the side-wall surface states, which also suppress the dark current to 11 pA. In addition, the photo response and the UV to visible rejection ratio of the PD with H₂O₂ passivation process are enhanced to 8.1×10^-3 A/W and 2.3×10³ when the PD is biased at -10 V. The noise equivalent power and the detectivity are determined to be 1.63×10^-8 W and 1.33×10⁸ cmHz^0.5W^-1. The simple passivation technique improves the AlGaN/GaN UV PD performances effectively.

Comparative studies of AlGaN/GaN MOS-HEMTs with stacked gate dielectrics by the mixed thin film growth method

This paper reports Al0.27Ga0.73N/GaN metal–oxide–semiconductor high electron mobility transistors (MOS-HEMTs) with stacked Al2O3/HfO2 gate dielectrics by using hydrogen peroxideoxidation/sputtering techniques. The Al2O3 employed as a gate dielectric and surface passivation layer effectively suppresses the gate leakage current, improves RF drain current collapse and exhibits good thermal stability. Moreover, by stacking the good insulating high-k HfO2 dielectric further suppresses the gate leakage, enhances the dielectric breakdown field and power-added efficiency, and decreases the equivalent oxide thickness. The present MOS-HEMT design has demonstrated superior improvements of 10.1% (16.4%) in the maximum drain–source current (IDS, max), 11.4% (22.5%) in the gate voltage swing and 12.5%/14.4% (21.9%/22.3%) in the two-terminal gate–drain breakdown/turn-on voltages (BVGD/VON), and the present design also demonstrates the lowest gate leakage current and best thermal stability characteristics as compared to two reference MOS-HEMTs with a single Al2O3/(HfO2) dielectric layer of the same physical thickness.

Investigation of Temperature-Dependent Characteristics of AlGaN/GaN MOS-HEMT by Using Hydrogen Peroxide Oxidation Technique

This paper investigates the temperature-dependent performances of AlGaN/GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT). The gate dielectric layer and surface passivation layer are formed by the H2O2 oxidation technique. The gate dielectric quality is estimated by the breakdown electric field (EBD) and low-frequency noise. The capacitance-voltage (C-V) hysteresis characteristics of MOS and Schottky diodes at 300/480 K are also studied. An appropriate thermal model is used to investigate the self-heating effect and calculate the effective channel temperature (Teff). The dc performances of the present MOS-HEMT are improved at 300/480 K, as compared with a Schottky-barrier HEMT (SB-HEMT), including output current density, maximum extrinsic transconductance (gm,max), gate voltage swing, gate-drain leakage current (IGD), specific ON-resistance (RON), three-terminal OFF-state breakdown voltage (BVOFF), and subthreshold swing. Factors that cause IGD and BVOFF are analyzed by the temperature-dependent measurement. The passivation effect of the present MOS-HEMT is also confirmed by the surface leakage measurement. The devised MOS-HEMT demonstrates superior thermal stability to the reference SB-HEMT. The present-design is promising for high-temperature electronic applications.

TiO2-dielectric AlGaN/GaN/Si metal-oxide-semiconductor high electron mobility transistors by using nonvacuum ultrasonic spray pyrolysis deposition

High-k TiO₂-dielectric Al_0.25Ga_0.75N/GaN metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs) grown on Si substrates by using nonvacuum ultrasonic spray pyrolysis deposition technique are reported for the first time. The effective oxide thickness is 1.45 nm with layer thickness/dielectric constant of 20 nm/53.6. Pulse I-V and low-frequency noise spectra (1/f) are conducted to characterize the interface property. The gate leakage current I_GD is decreased by three orders at V_GD = -50 V as compared with a reference Schottky-gate device. Superior device characteristics are achieved for the present MOS-HEMT (Schottky-gate HEMT) for the gate dimensions of 1 μm × 100 μm including drain-source current density I_DS at V_GS = 0 V (I_DSS0) of 384 (342) mA/mm, maximum I_DS(I_DS, _max) of 650 (511) mA/mm, maximum extrinsic transconductance (g_m, _max) of 107 (110) mS/mm, two-terminal gate-drain breakdown voltage (BVGD) of -155 (-105) V, turn-ON voltage (VON) of 3.8 (1.8) V, ON-state breakdown (BVDS) of 139 (94) V, gate-voltage swing of 2.7 (1.7) V, and ON/OFF current ratio (I_ON/I_OFF) of 4.5 x 10⁵(3.5 x 10²).

Comparative studies of MOS-gate/oxide-passivated AlGaAs/InGaAs pHEMTs by using ozone water oxidation technique

Al0.22Ga0.78As/In0.24Ga0.76As pseudomorphic high-electron-mobility transistors (pHEMTs) with metal-oxide-semiconductor (MOS)-gate structure or oxide passivation by using ozone water oxidation treatment have been comprehensively investigated. Annihilated surface states, enhanced gate insulating property and improved device gain have been achieved by the devised MOS-gate structure and oxide passivation. The present MOS-gated or oxide-passivated pHEMTs have demonstrated superior device performances, including superior breakdown, device gain, noise figure, high-frequency characteristics and power performance. Temperature-dependent device characteristics of the present designs at 300–450 K are also studied.

Investigations of TiO 2 –AlGaN/GaN/Si-Passivated HFETs and MOS-HFETs Using Ultrasonic Spray Pyrolysis Deposition

Comparative studies for TiO₂-passivated Al_0.25Ga_0.75N/GaN heterostructure FETs (HFETs) and TiO₂-dielectric MOS-HFETs using nonvacuum ultrasonic spray pyrolysis deposition technique are made. Optimum device performances are obtained by tuning the layer thickness of TiO₂ to 20 nm. High relative permittivity (k) of 53.6 and thin effective oxide thickness of 1.45 nm are also obtained. Pulse-IV, Hooge coefficient (α_H), Transmission Electron Microscopy, and atomic force microscope have been performed to characterize the interface, atomic composition, and surface flatness of the TiO₂ oxide. Superior improvements for the present TiO2dielectric MOS-HFET/TiO₂-passivated HFETs are obtained, including 47.6%/23.8% in two-terminal gate-drain breakdown voltage (BV_GD), 111%/22.2% in two-terminal gate-drain turnON voltage (V_ON), 47.9%/39.4% in ON-state breakdown (BV_DS), 12.2%/10.2% in drain-source current density (I_DS) at V_GS = 0 V (I_DSS0), 27.2%/11.7% in maximum I_DS (I_DS,max), 3/1-order enhancement in ON/OFF current ratio (I_ON/I_OFF), 58.8%/17.6% in gate-voltage swing linearity, 25.1%/13.2% in unity-gain cutoff frequency (f_T), 40.6%/24.7% in maximum oscillation frequency (f_max), and 33.8%/15.6% in power-added efficiency with respect to a Schottky-gated HFET fabricated on the identical epitaxial structure. The present MOS-HFET has also shown stable electrical performances when the ambient temperature is varied from 300 to 450 K.