Electric field strength and temperature dependence of conduction relaxation in AlGaN/AlN/GaN 2D electron gas
Electrical pulses of ns duration were applied parallel to the interfaces of AlGaN/AlN/GaN samples with a two-dimensional gas channel and an ultra-thin AlN spacer to create electric fields with strength up to 80 kV/cm. Conduction relaxation of the two-dimensional electron gas was measured after the high voltage pulses in temperature range from 86 to 293 K. Results of the conduction relaxation obtained in ns time scale were approximated by an expression containing two exponential components with different time constants. The time constants were chosen to correspond to the relaxation process in the field range from 40 to 60 kV/cm at various temperatures. Analysis of obtained expressions showed that the smaller constant τ1 slightly depended on temperature and the applied electric field and this was attributed to the electron release after the capture of hot electrons into shallow traps located in the AlN spacer or the AlGaN/AlN interface. The greater constant τ2, which appreciably depends both on electric field and temperature, we attribute to electron thermal release after the capture of hot electrons in the GaN layer. Also, the electrons can be thermally released from the centres in GaN present due to fluctuations of the bottom of the conduction band. The activation energy associated with the thermal processes is evaluated.
Keywords: AlGaN/AlN/GaN, pulsed I–V measurement, high electric field effects, conduction relaxation
PACS: 65.40.-b, 71.55.Eq, 72.20.Ht, 73.50.Fq