High carrier concentration in high Al‐composition AlGaN‐channnel HEMTs

Abstract

High Al‐composition (Al = 51%) and low Al‐composition (Al = 20%) AlGaN‐channel high‐electron‐mobility transistors (HEMTs) on AlN layers with very high carrier concentration were demonstrated. In two types of HEMTs, 2‐dimensional electron gases (2DEG) were clearly observed and peak carrier concentration and sheet carrier concentration were approximately 1020 cm‐3 and higher than 2 × 1013 cm‐2, respectively. From the X‐ray diffraction (XRD) measurements, it was observed that the AlGaN channel layers on the AlN layers were partially relaxed and the degree of relaxation decreased with increasing Al‐composition of AlGaN channel layers. Therefore the misfit dislocations in the high Al‐composition HEMTs were considered to be lower than those in the low Al‐composition HEMTs. Furthermore, it was revealed that very high Al‐composition of AlGaN barrier layers can be grown coherently on the AlGaN channel layers in consequence of the partly relaxation of the AlGaN channel layers, which of lattice constants of a‐axis were smaller than that of fully relaxed AlGaN channel layers. Therefore very high carrier concentration of 2DEG can be obtained in spite of the high Al‐composition of AlGaN channel layers. We considered that this high carrier concentration of 2DEG was necessary to demonstrate high Al‐composition AlGaN‐channel HEMTs. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electronic Transport Properties in AlInGaN/AlGaN Heterostructures

“…1–7are experimental data of AlGaN/AlGaN heterostructures from Refs. , and squares labeled as Nos. 8–9 are data of InAlN/AlGaN heterostructures from Refs.…”

“…Sanyam Bajaj et al realized a high electron mobility transistor (HEMT) with large threshold voltage of over 3 V on the basis of high composition AlGaN/AlGaN heterostructure. In recent years, some groups employ the AlGaN or AlN barrier layer in AlGaN channel HFETs to further improve the breakdown voltage, and other groups make a full use of the merit of nearly lattice‐matched heterostructures with InAlN barrier . Recently, our group reported a lattice‐matched InAlN/AlGaN heterostructures grown on sapphire substrate by pulsed metal organic chemical vapor deposition.…”

Enhancement of two‐dimensional electron gases in AlGaN‐channel high‐electron‐mobility transistors with AlN barrier layers

“…The degree of lattice relaxation for AlGaN channel layers on AlN layers has been discussed previously in Refs. 15, 16, the degree of relaxation for AlGaN‐channel HEMTs was discussed. Our result was almost consistent with those stated in the references.…”

Ultra-wide band gap AlGaN polarization-doped field effect transistor

“…Ultra-wide band gap (UWBG) semiconductors are attractive for high voltage power electronics [1][2][3][4][5][6] and high power rf electronics because the power density of these devices is expected to scale aggressively with band gap energy (E g ). For example, the lateral figure-of-merit (LFOM) for power switching increases as the square of the critical electric field (E crit ), 5) implying that LFOM increases E 5 g .…”