PECULIARITIES OF ULTRASOUND EFFECT ON 2DEG AND 3DEG CHARGE CARRIERS ELECTRONIC TRANSPORT IN GaN/AlGaN/GaN/AlN HETEROSTRUCTURES

Abstract

We have conducted the temperature and amplitude dependencies of the charge carriers concentration and its mobility analysis in GaN/Al0,2Ga0,8N/GaN/AlN on sapphire structures growing MOCVD method under the ultrasonic loading (longitudinal waves, fUS = 9 MHz). We found out the temperature peculiarities of electronic characteristics changes, it is allowed us to consider our system as complex with parallel conduction channels. In order to study the effect of ultrasound loading separately on both the flow of 3DEG and 2DEG charge carriers, a mathematical operation of separating these flows was carried out. It is shown, that at high temperatures (Т ˃ 200 K), 3DEG conductivity prevails, which has a thermal activation character and is described by the acoustically induced transformation of the metastable DX center. At temperatures (T ˂ 150K), 2DEG conductivity prevails. Thus, AlGaN/GaN and GaN/AlGaN boundaries can exhibit 2DEG conductivity (σ2D), while film layers (GaN buffer and AlGaN barrier layer are 3DEG conductivity (σ3D)). In the AlxGa1-xN structures containing DX centers, under US loading, there is a periodic change in the distance between the positions of the donor atom. Here, the determining mechanism is tunneling, the nature of which is related with dislocations. The horizontal sections observed in the experiment arise as a result of the tunnel emission of charge carriers through the quasi-resonant level. It was established that 3DEG and 2DEG charge carriers differ in the nature of temperature changes in concentration (with increasing temperature, there is an increase in 3DEG concentration and independence from temperature in 2DEG concentration) and mobility (decrease in 3DEG, but increase in 2DEG). It is shown that the influence of ultrasound in both cases, both for 3DEG and for 2DEG, of charge carriers is qualitatively similar - there is an increase in the 3DEG and 2DEG carriers concentration and a decrease in the absolute values of 3DEG and 2DEG mobility. Acoustically induced changes in electrical parameters most likely occur near dislocations that actively interact with ultrasonic waves.