Abstract
It has previously been reported that epitaxial growth of ZnO can be obtained at low temperatures by atomic layer deposition (ALD) onto a GaN (0001-Ga) surface, corresponding to a ~2.3% compressive lattice mismatch of the deposited ZnO. The question addressed here is the atomic ordering of deposited ZnO as a function of the lattice mismatch between ZnO and several single-crystal seeding surfaces. We have deposited ZnO using ALD onto either the (111) cubic or (0001) hexagonal surfaces of a set of available single-crystal substrates (GaAs, InP, GaN, SiC), for which the lattice mismatch varies over a wide range of values, positive and negative. It is found that deposition onto surfaces with very high extensive lattice mismatch (GaAs, InP) leads to polycrystalline ZnO, similar to the configuration obtained on an amorphous SiO2 surface. In contrast, ZnO ALD deposition onto both 2H-GaN (0001-Ga) and 4H-SiC (0001-Si) surfaces with lower and compressive mismatch leads to epitaxial ordering over the whole substrate temperature range of 180–250 °C.
Highlights
The progressive availability of an expanding range of semiconductor heterojunctions over the second part of the last century has paved the way to many of the present key devices for electronics and opto-electronics
This paper reports on a preliminary work which can be considered as a first step towards a future demonstration of new functional exogenic heterojunctions between two wide-bandgap compound semiconductors: on one side ZnO, which belongs to the II-VI family, and, on the other side, either the III-V GaN or the group IV 4H-SiC
atomic layer deposition (ALD) growth of ZnO was performed at temperatures ranging from 180–250 ◦C on an amorphous native silicon oxide surface of a silicon reference substrate
Summary
The progressive availability of an expanding range of semiconductor heterojunctions over the second part of the last century has paved the way to many of the present key devices for electronics and opto-electronics. All light-emitting diodes (LEDs) and laser diodes, together with the highest-performance microwave transistors and photodetectors, include at least one such heterojunction and there is a strong motivation in further extending the range of functional heterojunctions available for the design and manufacturing of new higher-performance devices. All the heterojunctions used today within the active parts of successful devices are isogenic heterojunctions, meaning that both semiconductor materials belong to the same chemical family, such as Group IV, III-V or II-VI. One possible reason is that for such exogenic heterojunctions every single chemical element of each semiconductor material can behave as a doping element within the other material. Any diffusion of chemical elements from one material into the other can dramatically change the doping profile and subsequently the electric field profile within the heterostructure
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