Mobility limiting scattering mechanisms in nitride-based two-dimensional heterostructures with the InGaN channel

Abstract

The scattering mechanisms limiting the carrier mobility in AlInN/AlN/InGaN/GaN twodimensional electron gas (2DEG) heterostructures were investigated and compared with devices without InGaN channel. Although it is expected that InGaN will lead to relatively higher electron mobilities than GaN, Hall mobilities were measured to be much lower for samples with InGaN channels as compared to GaN. To investigate these observations the major scattering processes including acoustic and optical phonons, ionized impurity, interface roughness, dislocation and alloy disorder were applied to the temperature-dependent mobility data. It was found that scattering due mainly to interface roughness limits the electron mobility at low and intermediate temperatures for samples having InGaN channels. The room temperature electron mobilities which were determined by a combination of both optical phonon and interface roughness scattering were measured between 630 and 910 cm 2 (V s) −1 with corresponding sheet carrier densities of 2.3-1.3 × 10 13 cm −2. On the other hand, electron mobilities were mainly limited by intrinsic scattering processes such as acoustic and optical phonons over the whole temperature range for Al0.82In0.18N/AlN/GaN and Al0.3Ga0.7N/AlN/GaN heterostructures where the room temperature electron mobilities were found to be 1630 and 1573 cm 2 (V s) −1 with corresponding sheet carrier densities of 1.3 and 1.1 × 10 13 cm −2 , respectively. By these analyses, it could be concluded that the interfaces of HEMT structures with the InGaN channel layer are not as good as that of a conventional GaN channel where either AlGaN or AlInN barriers are used. It could also be pointed out that as the In content in the AlInN barrier layer increases the interface becomes smoother resulted in higher electron mobility.

Electron transport properties in Al0.25Ga0.75N/AlN/GaN heterostructures with different InGaN back barrier layers and GaN channel thicknesses grown by MOCVD

“…The IFR has been treated as a combined scattering mechanism which includes effects of all interfaces. The strong effect of IFR can be attributed to the InGaN layer's growth quality, which is also consistent with the literature 15–17.…”

Modeling charge density in AlGaN/AlN/InGaN/GaN-based double heterostructures including InGaN layer strain relaxation

“…In spite of some minor deviations that can be related to experimental uncertainties, the proposed model is able to match the available experimental results well. Being generic in nature, this model also applies to InAlN/InGaN/GaN heterostructure designs [36][37][38][39]. This is because the surface state parameters of an InAlN barrier layer is already available [40].…”

Theoretical Investigation on Electron Mobility in AlInGaN/InGaN Heterostructures

“…Several attempts have also been made to elucidate the transport mechanisms in InGaN channel HFETs. Gökden investigated the carrier mobility in AlInN/AlN/InGaN/GaN heterostructures and compared with devices without InGaN channel. The results revealed that the main scattering limits the electron mobility at low and intermediate temperature is interface roughness for heterostructures having InGaN channels.…”