Electrical Characteristic of AlGaN/GaN High-Electron-Mobility Transistors With Recess Gate Structure

Abstract

AlGaN/GaN high-electron-mobility transistors (HEMTs) with nonrecess and recess gates are simulated by solving a set of drift-diffusion equations for electrostatic potential and electron-hole concentrations with selfheating model. The approach is first calibrated for both HEMT devices with experimentally measured data, to provide the best accuracy of the simulation. Recess gate device suffers from high potential to the channel, increased parasitic resistances, and deep level traps in barrier due to surface roughness. In addition, selective thinning of the barrier and increase parasitic resistance results in 17% reduction on the carrier concentration. The carrier mobility degradation due to surface roughness and electron velocity lessen due to high electric field result shrinkage of current density with considerable shift of the threshold voltage toward positive value. Even though transconductance does not seems to be remarkably changed for 3-nm recess gate, its value increases on deeper recess. This paper reveals that surface roughness is crucial issue that has dominant role behind the low current density in the recess gate structure. The detail physical understanding of the recess technology will be helpful to minimize the performance deterioration of the explored devices.

Analytical Model for Two-Dimensional Electron Gas Charge Density in Recessed-Gate GaN High-Electron-Mobility Transistors

“…To validate this work, the simulation results and experimental data 10 for the I D -V G transfer and I D -V D characteristics for both structures, viz. the non-recessed and recessedgate GaN HEMTs, are compared.…”

“…Figure 1 shows a schematic of an experimental GaN HEMT with the recessed-gate structure. 10 The epitaxial structure consists of a 15.6-nm-thick AlGaN barrier layer with Al mole fraction x = 0.27 on a 2-μm-thick GaN buffer layer grown on a sapphire substrate. The devices are fabricated with Ti/Al/Ni/Au (20/120/20/70 nm) ohmic metallization at the source and drain.…”

“…The recessed-gate structure is one of the approaches for designing E-mode GaN HEMTs for use in power electronic applications. 10 Understanding the physical mechanisms behind the formation of the 2DEG is crucial to model the 2DEG charge density under the gate and to device design. 11 Experimental research has shown that the presence of donor states at the AlGaN surface is the main source of the electrons in the 2DEG.…”

Design and Simulation of High Performance Lattice Matched Double Barrier Normally Off AlInGaN/GaN HEMTs

“…Similarly, recess gate is addition technology used in proposed HEMT, mobility attributed to surface roughness scattering was additionally solved with high priority. The details of mobility parameters used during simulation are listed in Table 2 and dependency of mobility of the device on surface roughness and correlation length were explained in our earlier works [13]- [14]. Since ohmic contact resistance plays a vital role in the device performance, low ohmic contacts are set up by designing n-type heavily doped GaN and AlInGaN regions under that source and drain.…”

Channel Characteristics of InAs/AlSb Heterojunction Epitaxy: Comparative Study on Epitaxies with Different Thickness of InAs Channel and AlSb Upper Barrier

“…So far, lots of research on III-V epitaxial materials focus on GaN/AlGaN, InAlAs/InGaAs, etc. [6][7][8]. However, studies on InAs/AlSb epitaxial materials are not broad, with few results [9][10][11][12].…”