Li-Hsien Huang

AlGaN/GaN Metal–Oxide–Semiconductor High-Electron Mobility Transistors Using Oxide Insulator Grown by Photoelectrochemical Oxidation Method

A photoelectrochemical oxidation method was used to directly grow oxide layer on AlGaN surface. The annealed oxide layer exhibited beta-Ga₂O₃ and alpha-Al₂O₃ crystalline phases. Using a photoassisted capacitance-voltage method, a low average interface-state density of 5.1 times 10¹¹ cm^-2. eV^-1 was estimated. The directly grown oxide layer was used as gate insulator for AlGaN/GaN MOS high-electron mobility transistors (MOS-HEMTs). The threshold voltage of MOS-HEMT devices is -5 V. The gate leakage currents are 50 and 2 pA at forward gate bias of VGS = 10 V and reverse gate bias of V_GS = -10 V, respectively. The maximum value of g_m is 50 mS/mm of VGs biased at -2.09 V.

High frequency and low frequency noise of AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors with gate insulator grown using photoelectrochemical oxidation method

The AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors, which are fabricated using gate insulators directly grown by photoelectrochemical oxidation method, were studied for rf and low frequency noise applications. The drain-source current in saturation (IDSS) and maximum extrinsic transconductance gm(max) are 580 mA/mm and 76.72 mS/mm, respectively. The unity gain cutoff frequency (fT) and maximum frequency of oscillation (fmax) are 5.6 and 10.6 GHz, respectively. Furthermore, the low frequency noise in saturation region is measured and fitted well by 1/f law up to 10 kHz.

Investigation and Analysis of AlGaN MOS Devices with an Oxidized Layer Grown Using the Photoelectrochemical Oxidation Method

A photoelectrochemical oxidation method was used to directly oxidize an AlGaN layer as the oxide layer of metal-oxide-semiconductor (MOS) devices. The crystal phases of the oxide films were analyzed by X-ray diffraction (XRD) measurement. The oxide films have a better stability and crystallization after annealing in O 2 ambient at 700°C for 2 h. The binding configurations of the oxide films were analyzed by X-ray photoelectron spectroscopy (XPS). According to the results of XPS, XRD, and secondary ion mass spectrometry (SIMS) measurements, the main components of the oxide films consist of Ga 2 O 3 and Al 2 O 3 . The average interface state density (D it ) between the oxidized AlGaN layer and AlGaN semiconductor is 5.1 X 10 11 cm -2 eV -1 . The leakage current of resultant MOS devices with a 45 nm thick oxide layer is 45 nA and 69 pA at 5 and -15 V, respectively. The breakdown field is 2.2 MV/cm and 6.6 MV/cm at breakdown voltage of 10 and -30 V, respectively.

Photoelectrochemical Function in Gate-Recessed AlGaN/GaN Metal–Oxide–Semiconductor High-Electron-Mobility Transistors

Photoelectrochemical (PEC) wet etching and oxidation methods were used for fabricating gate-recessed AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs). The AlGaN layer was recessed by the PEC wet etching method. The PEC oxidation method was then performed to directly grow an oxide film on the recessed surface of the AlGaN layer as gate dielectric film and passivation of the surface. The gate-recessed AlGaN/GaN MOS-HEMTs exhibited a saturation drain-source current of 642 mA/mm at VGS = 0 V, a maximum extrinsic transconductance of 86 mS/mm, and an off-state breakdown voltage of larger than -100 V.

GaN-based p-type metal-oxide–semiconductor devices with a gate oxide layer grown by a bias-assisted photoelectrochemical oxidation method

In this work, a bias-assisted photoelectrochemical (PEC) oxidation method was used to form an oxide insulator for GaN-based p-type metal-oxide?semiconductor (MOS) devices. The inversion breakdown and accumulation breakdown fields of the resulting GaN p-type MOS devices were 11.6 MV cm?1 and 3.7 MV cm?1, respectively. The interface-state density of the GaN p-type MOS devices was 4.18 ? 1011 cm?2 eV?1 obtained by a photo-assisted capacitance?voltage measurement method. In addition, the negative fixed oxide charge of 2.4 ? 1012 cm?2 eV?1 was also estimated.

Flicker Noises of AlGaN/GaN Metal-Oxide-Semiconductor High Electron Mobility Transistors

AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) with gate insulators grown using the photoelectrochemical oxidation method were fabricated in this work. The pinch-off voltage, maximum extrinsic transconductance, and drain-source saturation current at V GS = 0 V were -9 V, 88.20 mS/mm, and 665 mA/mm, respectively. When the MOS-HEMTs operated at V GS = -20 and 20 V, the gate leakage current was only 31 and 960 nA, respectively. The normalized noise power spectra of MOS-HEMTs operated in the linear region and the saturation region were fitted well by 1/f γ law from 4 Hz to 10 kHz. The exponent γ values were all closed to unity and independent of V GS . In the linear region (V DS = 2 V) at V GS = -8 V and V GS = 2 V, the α ch and α s estimated at a frequency of 100 Hz were 8.69 × 10 -6 and 9.29 × 10- 5 , respectively. The α ch and α s estimated in the saturation region (V DS = 10 V) at V GS = -8 V and V GS = 2 V at a frequency of 100 Hz were 1.61 × 10- 4 and 2.08 × 10 -3 , respectively. The normalized noise power density was a function of V -1 G , V -3 G , and V 0 G corresponded to the three regions of V G ≤ 3 V (V GS ≤ -6 V), 3 V ≤ V G ≤ 9 V (-6 V ≤ V GS ≤ 0 V), and V G ≤ 9 V (V GS ≤ 0 V), respectively, where V G was the effective gate bias defined as (V GS - V off ).

Investigation of AlGaN/GaN/AlGaN metal -oxide-semiconductor high electron mobility transistors

A photoelectrochemical (PEC) oxidation method was used to grow oxide films on AlGaN surface directly as gate insulator for AlGaN/GaN/AlGaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs). The threshold voltage of AlGaN/GaN/AlGaN MOS-HEMT devices is -3.5 V The gate leakage current is 1.8 times 10-5 A at reverse gate bias of VGS = -10 V. Maximum value of gm is 53.8 mS/mm biased at VGS = -0.87 V. The current collapse is not obvious in the MOS-HEMT devices.

Investigation and fabrication of AlGaN/GaN MOS- HEMTs with gate insulators grown by photoelectrochemical oxidation method

AlGaN/GaN MOS-HEMTs with gate insulators directly grown using photoelectrochemical (PEC) oxidation method were investigated. The gate length and the gate width is 1 μm and 50 μm, respectively. The drain-source saturation current (VGS=0 V) and the threshold voltage of AlGaN/GaN MOS-HEMTs is 580 mA/mm and -9 V, respectively. The maximum extrinsic transconductance is 76.72 mS/mm operated at VGS=- 5.1 V and VDS=10 V. The forward breakdown voltage and reverse breakdown voltage is 25 V and larger than -100 V, respectively. When the VGS=- 60 V and 20 V, the leakage current was 102 nA and 960 nA, respectively. The low frequency noise characteristics were also measured and studied. The Hooges coefficient estimated at VGS=0 V. When VDS is 10 V and 2 V at frequency of 100 Hz, the Hooges coefficient is 1.25×10-3 and 5.69×10-4, respectively.

AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors using directly grown oxide layer

A photoelectrochemical oxidation method was used to directly grow oxide film on the Al_0.15Ga_0.85N as the insulation film of the AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs). The gate leakage current at reverse bias of V_GS= -7V is WnA. Even the reverse bias is V_GS=-60V, the leakage current is only 102 nA. An unity gain cutoff frequency (f_T) of 5.6 GHz and a maximum frequency of oscillation (f_max) of 10.6 GHz were measured. These electrical performances are much better than those of GaN-based conventional MES-HEMTs.

Investigation of AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors using Photoelectrochemical Oxidation Method

A photoelectrochemical (PEC) oxidation method was used to directly grow oxide films on AlGaN surface as gate insulator for AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs). The threshold voltage of MOS-HEMT devices is -5 V. The gate leakage current is 50 pA and 20 pA at forward gate bias of Vgs=10 V and reverse gate bias of Vgs=-10 V, respectively. Maximum value of gm is 50 ms/mm of Vgs biased at -2.09 V.