High-temperature transport properties of 2DEG in AlGaN/GaN heterostructures

Abstract

Transport properties of the two-dimensional electron gas (2DEG) in fully strained and partially strain-relaxed Al 0.22 Ga 0.78 N/GaN heterostructures at temperatures from 300 to 680 K have been investigated by Hall effect measurements. The 2DEG mobility was found to decrease rapidly with increasing temperature at the initial stage and then decrease slowly as temperature is further increased. Those features indicate strongly that the 2DEG mobility is primarily limited by LO phonon scattering processes at high temperatures. Meanwhile, the calculated results show that more electrons transfer to the higher-order sub-bands with increasing temperature, and hence the effect of screening on LO phonon scattering is weakened and the alloy scattering of the AlGaN layer on the 2DEG becomes stronger. Thus variation of 2DEG occupation in different sub-bands with increasing temperature also decreases mobility of the 2DEG.

High Temperature Operation of E-Mode and D-Mode AlGaN/GaN MIS-HEMTs With Recessed Gates

“…We believe AlGaN strain relaxation starts to occur at around 350 °C due to thermal stress. It has been reported in several studies that AlGaN barrier layers exhibit significant strain relaxation above 300 °C [3], [5], [20]. Since AlGaN strain relaxation involves reduction of the amount of 2DEG, it is the primary reason for the sudden increase of the D-mode device threshold voltage at high temperature, considering the temperature independence of gate capacitance for both E-mode and D-mode devices.…”

“…High temperature electronics are required in many industry applications, such as automotive, spacecraft, deep-well drilling, and engine systems [1]. However, high temperature operation of the electronic devices suffers from increase of the leakage current, poor stability, and degraded mobility [2], [3]. Gallium nitride (GaN) is one of the most promising candidates for the high temperature electronics, due to many advantageous properties such as large bandgap, high breakdown field, high saturation velocity, and high thermal stability [4]- [6].…”

Improved quasi‐physical zone division model with analytical electrothermal Ids model for AlGaN/GaN heterojunction high electron mobility transistors

“…The fundamental properties of GaN HEMTs that are affected by temperature mainly consist of the Schottky barrier height ϕ B , the band gap energy E g , the low-field mobility μ 0 , the maximal electron saturated velocity υ sat , and the heat conductivity k. One way to study the temperature effects on GaN HEMTs performance with regard to these properties is carried out involving solution of complicated numerical expressions. [5][6][7][8] However, these numerical simulations are very time consuming and difficult to incorporate in circuit simulators. In comparison, analytical model is preferred as it is length (L g ) in order to minimize the parasitic gate resistance.…”

Hall Sensors for Extreme Temperatures

“…The electron density of the 2DEG depends very weakly on temperature up to 300 °C [ 7 , 8 ], which means that up to this temperature stable 2DEG can be a basis for the preparation of HTHS. For this purpose both simple AlGaN/GaN heterojunctions [ 7 , 9 , 10 ] and field-effect transistor structures based on this heterojunction [ 11 – 13 ] were examined. The electron mobility of the 2DEG in the heterojunction is about 1,000 cm 2 /(Vs), and strongly decreases with an increase in temperature to a value of about 300 cm 2 /(Vs) at 300 °C [ 8 , 13 ].…”