Improved electrical properties of the two-dimensional electron gas in AlGaN/GaN heterostructures using high temperature AlN interlayers

Abstract

The electrical properties of two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures using high temperature (HT) AlN interlayers (ITs) grown on c-plane sapphire substrate by metal organic chemical vapor deposition (MOCVD) have been investigated. It is found that the electrical properties (electron mobility and sheet carrier density) are improved compared with those in the conventional AlGaN/GaN heterostructures without HT AlN ITs, and the improved 2DEG properties result in the reduction of the sheet resistance. The results from high resolution X-ray diffraction (HRXRD) and Raman spectroscopy measurements show that HT AlN ITs increase the in-plane compressive strain in the upper GaN layer, which enhances the piezoelectric polarization in it and consequently causes increasing of 2DEG density at the AlGaN/GaN interface. Meanwhile, the compressive strain induced by HT AlN ITs leads to a less tensile strain in AlGaN barrier layer and causes positive and negative effects on the sheet carrier density of 2DEG, which counteract each other. The HT AlN ITs reduce the lattice mismatch between the GaN and AlGaN layers and smooth the interface between them, thus increasing the electric mobility of 2DEG by weakening the alloy-related interface roughness and scattering. In addition, the surface morphology of AlGaN/GaN heterostructures is improved by the insertion of HT AlN ITs. The reason for the improved properties is discussed in this paper. AlGaN/GaN heterostructures, electrical properties, two dimensional electron gas Citation:Xue J S, Hao Y, Zhang J C, et al. Improved electrical properties of the two-dimensional electron gas in AlGaN/GaN heterostructures using high temperature AlN interlayers.

Optical Properties of Monodispersed AlGaN Nanowires in the Single-Prong Growth Mechanism

“…and 668 cm -1 , respectively in the same Raman spectrum shows the two-mode behaviour of the random alloy that confirms again the presence of Al in the as-prepaired NWs and it is supporting stongly the EFTEM analysis carried out for the Al presence in the AlGaN NWs. GaN-Zone boundary phonon 11,39 420 GaN-Acoustic overtone 11,12,37,39 535 GaN-A 1 (TO) 11,12,37,39 558…”

“…GaN-E 1 (TO) GaN-E 1 (LO) 12,[37][38][39] (reported to be weak) 38 We have also performed polarization dependent resonant Raman scattering experiments for a single AlaGaN NW for further confirmation of crystalline orientation in the monodispersed sample. We have to resort to resonant Raman mode using the 325 nm (3.81 eV) excitation above the band gap of GaN (3.47 eV) 13 to maximize the Raman signal for a single NW in the sub-diffraction limit by invoking Fröhlich interaction of electron-phonon coupling.…”

“…As compared to the V Ga , the V Ga O N complex is much more stable. [13][14][39][40]42,47 3.19-3.23 DAP-LO The phonon replica of neutral donor-acceptor pair and which was observed because of the interaction between first order A 1 (LO) phonon with electron present in the DAP. 13,40,43 The three major factors affecting the blue shift in the band gap of the semiconductor nanomaterials are quantum confinement effect, 48,49 lowering temperature of the material, 50 and alloying with appropriate elements.…”