Stress optimization of AlN buffer in AlN/GaN/AlN Quantum well for DH-HEMT on SiC by PA-MBE

The stress of AlN buffer in AlN/GaN/AlN quantum well for double heterojunction high electron mobility transistor (DH-HEMT) heterostructure on SiC was optimized by varying the III/V ratio using PA-MBE. A relaxed AlN buffer enables the growth of strained GaN channel and strain-free AlN barrier for improved transport properties and reliability, respectively. AlN buffer layer with relaxation of 64% and a smooth surface morphology with RMS roughness 0.5 nm is achieved using two-step growth method. An average 2DEG sheet carrier density of $2.2 \times 10 ^{13}$ cm $^{-2}$ with carrier mobility of 534 cm $^{2} /$V.s is developed at the AlN/GaN heterointerface grown on the optimized AlN buffer.