Disorder effects in nitride semiconductors: impact on fundamental and device properties

Abstract

Semiconductor structures used for fundamental or device applications most often incorporate alloy materials. In “usual” or “common” III–V alloys, based on the InGaAsP or InGaAlAs material systems, the effects of compositional disorder on the electronic properties can be treated in a perturbative approach. This is not the case in the more recent nitride-based GaInAlN alloys, where the potential changes associated with the various atoms induce strong localization effects, which cannot be described perturbatively. Since the early studies of these materials and devices, disorder effects have indeed been identified to play a major role in their properties. Although many studies have been performed on the structural characterization of materials, on intrinsic electronic localization properties, and on the impact of disorder on device operation, there are still many open questions on all these topics. Taking disorder into account also leads to unmanageable problems in simulations. As a prerequisite to address material and device simulations, a critical examination of experiments must be considered to ensure that one measures intrinsic parameters as these materials are difficult to grow with low defect densities. A specific property of nitride semiconductors that can obscure intrinsic properties is the strong spontaneous and piezoelectric fields. We outline in this review the remaining challenges faced when attempting to fully describe nitride-based material systems, taking the examples of LEDs. The objectives of a better understanding of disorder phenomena are to explain the hidden phenomena often forcing one to use ad hoc parameters, or additional poorly defined concepts, to make simulations agree with experiments. Finally, we describe a novel simulation tool based on a mathematical breakthrough to solve the Schrödinger equation in disordered potentials that facilitates 3D simulations that include alloy disorder.

Energy Scales of Compositional Disorder in Alloy Semiconductors

“…In recent years, band-gap engineering has been applied to nitride semiconductors used in modern LEDs, 2 to perovskites for applications in photovoltaics, 3 to 2D systems, such as transition-metal dichalcogenides (TMDs), desired to miniaturize the corresponding devices toward nearly atomically thin dimensions, 4 and to organic disordered semiconductors 5 for Received: August 23, 2022 Accepted: November 24, 2022 applications in organic light-emitting diodes (OLEDs), organic thin-film transistors (OTFTs), and organic solar cells (OSCs). 5,6 The tunability of the semiconductor properties by alloying, however, has its price.…”

Effect of electric bias on trapping and release of excitons in GaN/(Al,Ga)N quantum wells

“…This points to the onset of the IX localization on the in-plane disorder potential at low IX densities. Indeed, due to strong builtin electric field in the growth direction, the amplitude of the localizing potential resulting from both (Al,Ga)N alloy composition and QW width fluctuations can reach 10 − 20 meV even in the best quality samples 52 .…”

Wigner-Weyl description of light absorption in disordered semiconductor alloys using the localization landscape theory

“…Caro et al [41]). Turning to (ii), comparing with experiment, the situation is also somewhat undecisive due to uncertainties on samples quality and geometries [42]. For instance, analysis of the Urbach tails in InGaN quantum wells (QWs) reported by Piccardo [9] and David [10] are significantly different.…”