CONDUCTION MECHANISM IN A METAL-INSULATOR-SEMICONDUCTOR STRUCTURE WITH A LOW-TEMPERATURE GAAS INSULATING LAYER

We report results of electrical characterisation of MIS diode structur es with Al metallisation, an insulating layer of low temperature grown (LT) GaAs on a n(+) GaAs substrate. The I-V characteristics at varyin g temperatures between 120 K and 285 K and a.c. conductivity measureme nts between 1 kHz and 13 MHz at room temperature were examined. The I- V characteristics were analyzed through the dependence of the diode id eality factor on temperature. Values between 2.8 and 4 were obtained, typical of tunneling through the depletion potential barrier in the n( +) GaAs at the interface. The high voltage part of the forward I-V cha racteristics indicates a low and weakly temperature dependent series r esistance of the diode, associated with carrier transport through LT-G aAs, characterised by an activation energy of 32 meV. The a.c. dynamic resistance in the high voltage part of the I-V characteristics decrea ses as a function of frequency and between 2 MHz and 13 MHz approximat ely follows omega(s) dependence with s = 0.65. These results are consi stently interpreted as the result of the transport of injected carrier s through the LT GaAs layer via a hopping mechanism involving defects. (C) 1997 Elsevier Science Ltd.