Influence of External Plane Stress on Electric Parameters of AlGaN/GaN HEMT Heterostructures

Herein, the influence of stresses on parameters of 2D electron gas (2DEG) in AlGaN/GaN high‐electron‐mobility transistor‐type heterostructures grown on sapphire substrate by metal–organic vapor‐phase epitaxy technique is presented. The as‐grown heterostructures as well as Schottky diodes fabricated in them are subjected to compressive stress. The custom stressing system induces a homogeneous state of compressive stress in the samples without causing electrical side effects. Time‐dependent heterostructures characteristics of electron concentration, electron mobility, and bandgap width are measured. Additionally, in the case of the Schottky diodes, current–voltage characteristics and charge flow in the contact are measured. The measurements are performed in cycles with and without applied stresses to determine the repeatability of effects and to separate the influence of thermal and electrical factors. Additionally, electrical simulations are performed using APSYS software package. The obtained results lead to conclusions that are different to those reported in existing literature, especially in regard to the time dependence of the measured effects, that is essential to proper explanation. It is also shown that a key role in the change of 2DEG parameters is played by deep surface states and interlayer piezoelectric effects. Finally, the anisotropic character of the derived relations is demonstrated.