Properties of Si-doped GaN films grown using multiple AlN interlayers

Electrical, optical, and structural properties of Si-doped GaN films grown on multiple AlN interlayers (IL) sandwiched between high-temperature (HT) GaN are presented. We show that as the number of AlN IL/HT GaN layers increases, the electron mobility increases in the top Si-doped GaN layer, showing a near doubling from 440 to 725 cm2 V−1 s−1. Cross-sectional transmission electron microscopy images reveal a significant reduction in the screw dislocation density for GaN films grown on the AlN IL/HT GaN layers. The symmetric and off-axis x-ray linewidths increase as the number of AlN IL/HT GaN layers increase, indicating a greater relative misalignment of the adjacent HT GaN layers. Photoluminescence spectra of undoped and Si-doped GaN films on the multiple AlN IL/HT GaN layers have small yellow-band intensity. Analysis based on a single-donor/single-acceptor model for the electrical conduction suggests that the improved electron mobility is the result of a reduced acceptor concentration in the top GaN film and that this acceptor may possibly be associated with threading screw dislocations in GaN.