Polarity control of ZnO films grown with high temperature N‐polar GaN intermediate layers by plasma‐assisted molecular beam epitaxy

Abstract

ZnO epilayers were grown on nitridated c-Al 2 O 3 substrates by plasma-assisted molecular beam epitaxy and the effect of the deposition temperature for GaN buffer and/or intermediate layers on the polarity of ZnO epilayer was investigated. First, it was found that the polarity of the ZnO epilayers grown on low temperature-grown GaN buffer and/or intermediate layers was uncertain and it became often +c polarity, i.e., Zn-polarity. This seems strange because the polarity of the GaN-underlying layer was -c polarity, i.e., N-polarity, and then the polarity of the under layer was not kept unchanged by the following epilayer. On the other hand, when the growth temperature of the GaN buffer/intermediate layer was increased above 850 °C, it was found that the polarity of the GaN layer was followed by the ZnO epilayers; the polarity became -c polarity, i.e., O-polarity. This reason was estimated by the effect of surface oxides on GaN which were formed just before the deposition of ZnO buffer layer on it.

Effect of GaN buffer layers on the polarity and properties of ZnO epilayers on nitrided c‐Al2O3 by MBE

“…The growth process was monitored by in-situ and real-time RHEED monitoring/analyzing system (kSA-400). This result was already reported in another work [9].…”

“…Further, it was found that the polarity of ZnO epilayers are strongly affected by the deposition temperatures of GaN buffers, i.e., nor-mally Zn-polarity (+c) for low-temperature (LT) buffer deposited at 650 o C and O-polarity (-c) for hightemperature (HT) buffer deposited at 850 o C [9]. Then, in this paper, we investigated how the GaN buffer layers affect their properties such as structural and optical properties in the ZnO epilayers.…”

GaN grown with InGaN as a weakly bonded layer

“…Both sample B and B InGaN show (0002) and ( 0004 14 This can be explained by the GaN overlayer in sample B inheriting the N polarity from the nitrided sapphire substrate. 15,16 This leads to an interesting and significant result that the nearly stress free GaN thin film with mirror-like morphology and single polarity can be obtained by inserting an appropriate InGaN interlayer.…”

Polarity Control of ZnO on N-Terminated GaN(0001) Surfaces

“…The experimental result for ZnO on an N-polarity GaN substrate has been shown. In fact, Roh et al 3) have recently shown that the growth behaviors of the ZnO layer on these what are different. They have shown that ZnO epilayers grown on low-temperature (LT) GaN layers typical exhibit Zn polarity, while those grown on high-temperature (HT) GaN layers typical exhibit O polarity.…”