AlGaN/GaN/InGaN/GaN DH-HEMTs with GaN channel layer grown at high temperature

¹ Beijing Optoelectronic Technology Lab, Beijing University of Technology, Beijing 100022, P.R. China
² Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, P.R. China
³ Xi’an Jiaotong University, Xi’an 710049, P.R. China

^a e-mail: xlwang@semi.ac.cn

Received: 25 September 2012
Revised: 22 October 2012
Accepted: 20 March 2013
Published online: 22 May 2013

Abstract

The AlGaN/GaN/InGaN/GaN double heterojunction high electron mobility transistors (DH-HEMTs) sample has been grown by MOCVD on (0 0 0 1) sapphire substrate. The structure features a 7 nm In_0.046Ga_0.954N interlayer determined by Rutherford backscattering (RBS). Since the polarization field in the InGaN interlayer is opposite to it in the AlGaN layer, an additional potential barrier is introduced between the two-dimensional electron gas (2DEG) channel and buffer, leading to enhanced carrier confinement and improved buffer isolation. The GaN layers between the AlGaN layer and InGaN interlayer are divided into two layers consisting of GaN channel layer which provides high mobility 2DEG grown at 1070 °C and GaN spacer layer grown at the same temperature as InGaN interlayer (800 °C) to prevent indium diffusion. RBS measurement confirms that the 3 nm GaN spacer layer isolates the InGaN interlayer well and free from diffusion. Hall measurement has been performed, the mobility as high as 1552 cm²/V s at room temperature is obtained and the sheet carrier density is 1.55 × 10¹³ cm⁻². The average sheet resistance is 331 Ω/sq, respectively. The mobility obtained in this paper is about 20% higher than similar structures reported.