Effect of Local Substrate Removal and Backside Al Heat Dissipation Layer on GaN-on-Si Device RF Performance

Abstract

This study investigates the influence of local substrate removal and the implementation of a backside Al heat dissipation layer on the radio frequency (RF) performance of GaN-on-Si devices. To optimize the RF properties of these devices by mitigating the influence of the parasitic capacitance layer between the AlN nucleation layer and the Si substrate by the local substrate removal process. Nevertheless, this removal reduces the heat dissipation path, elevating channel temperatures and reducing drain current and transconductance (G M ). To address this issue, an Al heat dissipation layer is deposited onto the device’s backside surface. Combining the LSR process and the Al heat dissipation layer improved power-added efficiency from 38.93% to 48.47% at a frequency of 3.5 GHz. By integrating the local substrate removal process with the backside Al heat dissipation layer, we increased power-added efficiency from 38.93% to 48.47 at a frequency of 3.5 GHz. At 200 μ s, the transient drain current ratio with and without stress voltage was measured at 0.914 for the conventional device and 0.997 for the LSR + Al device. The temperature-induced change in on-resistance (R on ) for the pure LSR devices is 10.08 mΩ °C, whereas the LSR devices with a 5 μ m Al layer on the backside exhibit a much lower slope of 1.78 mΩ °C −1 .