Al composition dependent structural and electrical properties of InAlGaN/GaN heterostructures

Abstract

InAlGaN/GaN heterostructures with various Al compositions have been grown on sapphire substrate using the metal organic chemical vapour deposition technique. The solid-to-gas phase ratio indicates a high Al incorporation efficiency. Atomic force microscopy reveals a smooth surface with the formation of hexagonal pits. The size and the density of the hexagonal pits increase with increasing Al mole fraction. The Hall effect and the capacitance–voltage (C–V) studies show the formation of a two-dimensional electron gas (2DEG) at the InAlGaN/GaN interface. A relatively higher Hall sheet carrier density compared with the 2DEG density estimated from the C–V profile indicates parallel conduction via the underlying GaN layer. It is observed that the 2DEG density decreases as a function of the Al composition and these results are discussed based on the increasing depth of the hexagonal pit and the background donor density.

Epitaxy and characterisation of AlInGaN heterostructures for HEMT application

“…3) show in all samples roughness values in the order of 2-3 nm RMS for a 10 µm x 10 µm scan area and about 1 nm RMS for a 2 µm x 2µm scan area. No visible hexagonal pits as reported in similar experiments [14] could be detected. Figure 4 The observed spectrum was taken at 19 K and shows GaN-related peaks and a weak AlInGaN near bandgap emission peak at 335 nm (3.71 eV).…”

“…Constitution analysis with several methods mentioned in Table 1 displays an increasing ratio between AlN and InN in the quaternary layers with rising GaN content. AlN, GaN and InN have binding energies of 11.52 eV, 8.92 eV and 7.72 eV, respectively [14]. The differences in bond strength for these nitride materials, a similar trend in adsorption strength and a lower enthalpy of mixing for Al-GaN [15], lead to competitive adsorption in favour of Ga atoms which will partly incorporate at the cost of In atoms.…”

“…1). [14]. The differences in bond strength for these nitride materials, a similar trend in adsorption strength and a lower enthalpy of mixing for AlGaN [15], lead to competitive adsorption in favour of Ga atoms which will partly incorporate at the cost of In atoms.…”

Performance Enhancement of Ultraviolet Light-Emitting Diodes by Incorporating a Thin Al(In)GaN Interlayer in Multiquantum-Well Region

“…Thus, MQW with a fixed AlGaN interlayer (LED-A) shows rougher surface and worse crystalline quality [19], which can also influence the PL optical properties [25]. The surface roughness can be further improved by using a graded AlInGaN interlayer (LED-C), which is mainly owing to the addition of indium as a surfactant into the AlGaN [23], [26]. In addition, AlInGaN layers have some advantages, such as In-segregation effect and reduced lattice mismatch with a lower internal field [8].…”

Quaternary nitride heterostructure field effect transistors

“…AlInN-based barrier layers suffer to some extent from granular morphology, increased roughness and alloy scattering due to clustering [7]. Other groups already employed quaternary structures with one constituent lower than 3 % [8,9]. Here, we study the application of quaternary layers outside these quasi ternary regimes and their structural and electrical properties.…”