Excess current in n⁺GaAsAl_xGa_1-xAsnGaAs heterojunctions

Current versus longitudinal stress characteristics with 〈100〉 stress direction for four n + GaAsAlx Ga1-xAsnGaAs heterojunc grown on (100) substrates are measured and compared with theory. Our samples have the AlGaAs barriers with aluminum concentrations x=0.30, 0.32, 0.50 and 0.80 and the thickness range from 300-400 Å. The agreement between theory and experiment is good, if we assume an X-valley shear deformation potential of 9.6 eV. However, x=0.32 and 0.50 samples need about 5 kbar of stress offset to match our experimental results with theory, which may be due to the excess current through impurities whose energy level is coupled to the X-valleys. © 1990.