Nearly-zero valence band and large conduction band offset at BAlN/GaN heterointerface for optical and power device application

Abstract

Wurtzite BAlN alloy with large bandgap is an emerging material system for UV optoelectronic and power devices. In this study, the BAlN/GaN heterojunction with a sharp interface and uniform distribution of the elements was formed by careful control of epitaxial conditions to avoid GaN desorption and parasitic reactions whose band alignment was then measured for the first time. The valence band offset (VBO) was found to be nearly-zero, i.e. −0.2 ± 0.2 eV, in the B 0.14 Al 0.86 N/GaN heterojunction by X-ray photoelectron spectroscopy. Additionally, the conduction band offset (CBO) is estimated at 2.1 ± 0.2 eV, which is the largest reported CBO among epitaxial GaN-based heterojunctions. In comparison to the type-I Al 0.75 Ga 0.25 N/GaN heterojunction (both Al 0.75 Ga 0.25 N and B 0.14 Al 0.86 N alloy have the same bandgap of 5.7 eV), the CBO and VBO of the B 0.14 Al 0.86 N/GaN heterostructure are significantly larger and smaller, respectively. The nearly-zero VBO and the very large CBO of the B 0.14 Al 0.86 N/ GaN heterojunction could potentially lead to considerable performance enhancement for GaN optoelectronics and power electronics devices.

Demonstration of single-phase wurtzite BAlN with over 20% boron content by metalorganic chemical vapor deposition

“…Due to their unique properties such as lattice, optical, and polarization constants, they are promising for potential applications in UV devices, distributed Bragg reflectors (DBRs), power electronic devices, radiation tolerant electronics, and other optoelectronic components. [1][2][3][4][5][6][7][8][9] However, at present many epitaxial challenges need to be addressed to achieve high quality and to increase the boron content while maintaining the wurtzite phase, such as phase separation, limited thin film thickness, and limited adatom diffusion length. [10][11][12][13][14][15] The boron content of the wurtzite BAlN alloys has been limited to less than 15% with a relatively small thickness of 100 nm, which greatly limits the device applications of the BAlN alloys.…”

BAlN alloy for enhanced two-dimensional electron gas characteristics of GaN/AlGaN heterostructures

“…Moreover, the lattice constant and polarization properties of the BAlN alloys have been studied, in which large variations of those important quantities were found [16][17][18] . The net heterointerface polarization charges of the strained AlxGa1-xN/GaN (0≤x≤1) heterostructures on relaxed GaN are much smaller compared to those of the strained AlxGa1- showing an extremely large conduction band offset between BAlN and (Al)GaN due to the type-II nature which is distinct from the type-I nature for the AlxGa1-xN/GaN (0≤x≤1) heterostructures [20,21] .…”

“…barrier layer shown in Figure 1a [22][23][24] . For the interlayers, various designs under consideration include: [20,21] .…”

“…The formation of the 2DEG amid the HEMT structures are mainly related to the heterointerface polarization difference and the band offset. The lattice constants, polarization parameters, and band offsets of the involved materials are from Refs [16,17,20,21] , from which it can be deduced that the B0. Figure 3, have the lowest 2DEG…”

Analytical study of effect of energy band parameters and lattice temperature on conduction band offset in AlN/Ga2O3 HEMT

“…Furthermore, higher charge confinement in the triangular well is anticipated based on higher energy difference between Ef and E0 [21]. It is worth mentioning that, some fraction, say 60 or 80 % and very rarely up to 100% [22], of the heterostructures' material bandgap difference appears as CBO. Therefore, while estimating ns, careful measurement of CBO (ΔEC) is important.…”