S. B. Dolmanan

AlGaN/GaN two-dimensional-electron gas heterostructures on 200 mm diameter Si(111)

This Letter reports on the epitaxial growth, characterization, and device characteristics of crack-free AlGaN/GaN heterostructures on a 200 mm diameter Si(111) substrate. The total nitride stack thickness of the sample grown by the metal-organic chemical vapor deposition technique is about 3.3 ± 0.1 μm. The structural and optical properties of these layers are studied by cross-sectional scanning transmission electron microscopy, high-resolution x-ray diffraction, photoluminescence, and micro-Raman spectroscopy techniques. The top AlGaN/GaN heterointerfaces reveal the formation of a two-dimensional electron gas with average Hall mobility values in the range of 1800 to 1900 cm2/Vs across such 200 mm diameter GaN on Si(111) samples. The fabricated 1.5 μm-gate AlGaN/GaN high-electron-mobility transistors exhibited the drain current density of 660 mA/mm and extrinsic transconductance of 210 mS/mm. These experimental results show immense potential of 200-mm diameter GaN-on-silicon technology for electronic devi...

High-Frequency Microwave Noise Characteristics of InAlN/GaN High-Electron Mobility Transistors on Si (111) Substrate

We report for the first time high-frequency microwave noise performance on 0.17-μm T-gate In_0.17Al_0.83N/GaN high-electron mobility transistors (HEMTs) fabricated on Si(111). The HEMTs exhibited a maximum drain current density of 1320 mA/mm, a maximum extrinsic transconductance of 363 mS/mm, an unity current gain cutoff frequency (f_T) of 64 GHz and, a maximum oscillation frequency [fmax ^(U)/ f_max (MSG)] of 72/106 GHz. The product f_max(U) × L_g=12.24 GHz· μm is the highest value ever reported for InAlN/GaN HEMTs on Si substrate. At V_d=4 V and V_g=-2.25 V, the device exhibited a minimum noise figure (NF_min) of 1.16 dB for 10 GHz and 1.76 dB for 18 GHz. Small variation of NF_min (<;0.5 dB) from 8% to 48% with I_Dmax (100-636 mA/mm) was observed.

Effects of AlN thickness on structural and transport properties of In-rich n-AlInN/AlN/p-Si(0?0?1) heterojunctions grown by magnetron sputtering

We have studied the effect of AlN buffer layers, having variable thicknesses in situ grown by rf-magnetron sputtering, on the structural and vibration dynamic properties of AlInN thin films grown by dc-magnetron sputtering on Si(0?0?1) substrates at 700??C. X-ray diffraction patterns reveal that an increase in thickness of the AlN buffer layer can significantly promote the textured growth orientation of AlInN(0?0?0?2)//Si(0?0?1) and improve the grain sizes of AlInN. They also reveal that the Al composition in the resultant AlInN thin film increases with the thickness of AlN; however, phase separations, which are usually observed in metal-organic chemical vapour deposition (MOCVD) growth of AlInN with similar Al compositions, are not detectable. Instead, uniform element distribution profiles along the growth direction of AlInN are detected by secondary ion-mass spectroscopy. Micro-Raman scattering spectra collected at room temperature exhibit three optical phonon features from the AlInN thin films, which, in terms of their evolutions with Al composition, can be assigned to AlInN , InN-like A1(LO), and AlN-like A1(LO), respectively, consistent with that recently observed in MOCVD grown In-rich AlInN. The solar cell based on n-AlInN/AlN/p-Si exhibits a typical diode-like dark I?V curve; however, its photocarrier collection is apparently suppressed due to the polarization charges at the junction interfaces.

Luminescence Properties of Photonic Crystal InGaN/GaN Light Emitting Layers on Silicon-on-Insulator

The photonic crystal InGaN/GaN light emitting diodes (LEDs) on thin silicon-on-insulator (SOI) substrates are demonstrated. Surface nanopatteming has been carried out on such LED layers and the processing conditions are varied to improve the outcoupling of visible emission. A substantial increase in the photoluminescence intensity is observed from LEDs on a thin SOI overlayer as compared to a similar structure grown on a thicker SOI. In addition, enhancement of the cathodoluminescence and electroluminescence intensity from such photonic crystal LEDs shows their potential in solid-state lighting.

In 0.17 Al 0.83 N/AlN/GaN Triple T-shape Fin-HEMTs with g m =646 mS/mm, I ON =1.03 A/mm, I OFF =1.13 µA/mm, SS=82 mV/dec and DIBL=28 mV/V at V D =0.5 V

We report the first 3D Triple T-gate InAlN/GaN nano-channel (NC) Fin-HEMTs on Si substrate with record high device performances at V_D as low as 0.5 V. Utilizing a T-gate approach on NC Fin-HEMT with stress engineered techniques, enhanced device transport properties with g_m=646 mS/mm, I_on=1.03 A/mm, I_OFF=1.13 μA/mm, I_ON/I_OFF~106, SS=82 mV/dec at V_D=0.5 V were achieved. In addition, the Fin-HEMT also exhibited 3.2 times lower DIBL of 28 mV/V. The dramatic improvement of device performance is due to the tensile stress induced by SiN passivation in the NC Fin-HEMT.

Influence of PECVD deposited SiN x passivation layer thickness on In0.18Al0.82N/GaN/Si HEMT

The influence of plasma enhanced chemical vapour deposited (PECVD) silicon nitride (SiN x ) passivation film thickness on In0.18Al0.82N/GaN/Si heterostructures and HEMTs has been investigated. The formation of Si3N4 was confirmed by x-ray photoelectron spectroscopy (XPS) measurements. X-ray reflectivity (XRR) measurements reveal that both the density and roughness of the SiN x film increase with increasing film thickness. With an increase in SiN x film thickness, a significant increase in two-dimensional electron gas (2DEG) density, drain current, extrinsic transconductance and negative threshold voltage shift of the In0.18Al0.82/GaN/Si HEMTs are observed. An optimal thickness of SiN x is ~100 nm and it yields a substantial increase in 2DEG density (~30%) with a minimum sheet resistance for In0.18Al0.82N/GaN/Si heterostructures. Furthermore, we correlate the observed SiN x film thickness-dependent electrical characteristics of In0.18Al0.82/GaN/Si HEMTs with the density of the SiN x film.

AlxGa1?xN/GaN heterostructures on a thin silicon-on-insulator substrate for metal?semiconductor?metal photodetectors

The authors demonstrate epitaxial growth of two-dimensional-electron-gas (2DEG)-based AlxGa1−xN/GaN heterostructures on a thin silicon-on-insulator (SOI) substrate. Cross-sectional transmission electron microscopy, high-resolution x-ray diffraction, photoluminescence, atomic force microscopy and ultraviolet (UV) micro-Raman spectroscopy measurements are performed to address the structural and interface properties of the epilayers on such a Si-based composite substrate. Device processing of Schottky metal–semiconductor–metal UV photodetectors is carried out to test the applicability of such a thin AlxGa1−xN layer on a GaN/SOI template for UV sensors. The high sensitivity response of such a 2DEG AlxGa1−xN/GaN heterostructure in the UV spectral range shows high potential for integration with SOI-based electronics and photonics.

Improved OFF-state breakdown voltage in AlGaN/GaN HEMTs grown on 150-mm diameter silicon-on-insulator (SOI) substrate

The AlGaN/GaN-based high-electron-mobility transistors (HEMTs) are suitable for discrete components in many high power and high frequency power electronics applications useful for communications, satellites, power amplifiers, inverters/converters for electric and/or hybrid vehicles. Presently, these devices are commonly grown on sapphire, silicon carbide, and recently on 100- to 200-mm diameter silicon substrates. For a large scale deployment of low cost GaN-based power electronic devices, silicon substrate offers tremendous opportunities due to mature back-end Si process technologies. However, GaN epilayers on large area Si substrates results in severe wafer bowing and cracking due to high thermal mismatch between nitride layer and the substrate. As an alternative to Si substrate, silicon-on-insulator (SOI) substrate has been used for the demonstration of GaN-based light emitting diodes (LEDs)[1]. To the best of our knowledge, the demonstration of AlGaN/GaN transistors on a thin SOI substrate is rather limited. In this study, we report on the growth and characteristics of AlGaN/GaN heterostructures (HSs) on 150-mm diameter Si(111) and SOI(111) substrates. In addition, fabrication of HEMTs and device characteristics will be discussed on the SOI platfrom.