A comparative study of wet etching and contacts on ((2)over-bar01) and (010) oriented beta-Ga2O3

Abstract

We report on the effect of beta-Ga2O3 crystal orientation on wet etching and Ohmic contact formation. The photochemical etching rate in KOH solutions of ((2) over bar 01) oriented, n-type bulk single crystals grown by the edge-defined film-fed growth method is similar to 3-4 times higher than for the (010) planes. The activation energy for etching was 0.498 eV and 0.424 eV for ((2) over bar 01) and (010) orientations, respectively, suggesting the etching is reaction-limited with the same rate-limiting step. Ti (2)00 angstrom)/Au (1500 angstrom) metallization deposited on the two different orientations and annealed at 450 degrees C showed Ohmic current-voltage (I-V) behavior for ((2) over bar 01) but rectifying characteristics for (010). For (010) Ga2O3, there exists 2 types of surfaces having Ga and O atomic densities of 0.58 and 0.87 x 10(15) cm(-2), respectively. By contrast, for ((2) over bar 01) Ga2O3 surfaces, there exist 2 types of surface, with each type terminated with only Ga or O. If the surface is terminated with 0, the dangling bond densities of 0 are 1.78 and 2.68 x 10(15) cm(-2), respectively. We found that ((2) over bar 01) oriented Ga2O3 is etched at higher rates and is easier to form Ohmic contacts than (010) Ga2O3. The higher density of oxygen dangling bonds on the ((2) over bar 01) plane correlates with the faster etch rates and pronounced Ohmic behavior from deposited metals. (C) Elsevier B.V. All rights reserved.