ELECTRICAL RESISTANCE OF CRACK-FREE GaN/AlN HETEROSTRUCTURE GROWN ON Si(111)

Abstract

This paper presents the electrical resistance of crack-free n-GaN/AlN/n-Si(111) diodes in relation to the temperature of the Al effusion cell for the growth of AlN intermediate layer (348 nm thickness) using radio-frequency molecular beam epitaxy (RF-MBE). The thickness of the unintentionally doped n-type GaN thin film is in the range of 63–100 nm. Aluminium (300 nm thickness) was sputtered onto the n-type GaN through a metal mask, followed by the 100 nm thick titanium (Ti) capping layer to obtain an ohmic contact. The back contact was created on the back surface of the Si substrate by evaporating indium (In) followed by thermal annealing at 400°C. We will consider the above as a device on an n-type Si(111) substrate, where the electron current flows from the Si substrate to the n-type GaN top layer. It was found that the current–voltage (I–V) characteristics depend on the various deposition temperature of the Al effusion cell for the growth of the AlN intermediate layer. In the forward bias region, where the electrons flow from Si(111) to the GaN top layer, we observe a threshold voltage of approximately 0.5 V for turning on a high current. The order of differential resistance magnitude was nearly a constant in the voltage range of 1.0 to 3.0 V.