Double Gaussian distribution of barrier heights and self-powered infrared photoresponse of InN/AlN/Si (111) heterostructure

InN epilayer has been grown by plasma-assisted molecular beam epitaxy on the AlN/n-Si (111) substrate. The self-powered photodetection has been carried out with an infra-red (IR) laser (lambda = 1550 nm, power density similar to 106: 2 mA= cm2), where a photoresponsivity was observed to be 3.36 mu A/W with response times in milliseconds from the InN/AlN/n-Si (111)-based semiconductor-insulator-semiconductor (SIS) interface. Furthermore, to elucidate the vertical electrical transport properties of the SIS interface, low-temperature electrical behavior has been investigated over a range of 100-400 K. Experimental studies revealed an abnormal increase in the barrier height and a decrease in the ideality factor with increasing temperature, suggesting inhomogeneous barrier heights across the heterojunctions. Such inhomogeneity behaviors have been successfully explained on the basis of thermionic emission theory, assuming the existence of a double Gaussian distribution of barrier heights at the heterostructure interface. Moreover, the SIS device structure exhibits mean barrier heights (phi wb0) of 1.11 and 0.63 eV, respectively, in two temperature regimes, indicating the presence of defect states and inhomogeneity at the interface, which is supported by the nonlinear behavior of the photocurrent with the power density.