PEALD-deposited crystalline GaN films on Si (100) substrates with sharp interfaces

Abstract

Polycrystalline gallium nitride (GaN) thin films were deposited on Si (100) substrates via plasma-enhanced atomic layer deposition (PEALD) under optimal deposition parameters. In this work, we focus on the research of the GaN/Si (100) interfacial properties. The x-ray reflectivity measurements show the clearly-resolved fringes for all the as-grown GaN films, which reveals a perfectly smooth interface between the GaN film and Si (100), and this feature of sharp interface is further confirmed by high resolution transmission electron microscopy (HRTEM). However, an amorphous interfacial layer (∼ 2 nm) can be observed from the HRTEM images, and is determined to be mixture of Ga x O y and GaN by xray photoelectron spectroscopy. To investigate the effect of this interlayer on the GaN growth, an AlN buffer layer was employed for GaN deposition. No interlayer is observed between GaN and AlN, and GaN shows better crystallization and lower oxygen impurity during the initial growth stage than the GaN with an interlayer.

Interfacial Tailoring for the Suppression of Impurities in GaN by In Situ Plasma Pretreatment via Atomic Layer Deposition

“…The formed IL between the nonpretreated GaN and the Si substrate has been determined to be mainly Ga x O y with minor GaN. 23 The high oxygen concentration in this IL might be the principal reason for the successive formation of an ∼18 nm thick amorphous GaN layer, hindering the crystallization of GaN. Herein, the pretreated GaN with much thinner (∼5.3 nm) amorphous transition GaN layer probably means a lower oxygen content in IL.…”

“…The detail experimental process and the optimized deposition parameters have been reported in our previous work. 23 For the GaN with pretreatment, in this case, the substrate surface was in situ pretreated for 600 s using A r /N 2 /H 2 (1:3:6) plasma prior to the deposition of GaN.…”

“…27 We have confirmed that oxygen impurity from the initial deposition of GaN can be reduced by inserting an AlN buffer layer. 23 More methods are necessary to suppress the impurities in GaN. Because ALD relies dramatically on surface reactions and the initial growth process ultimately influence the subsequent growth of film, we try to reduce the impurities by modifying the surface states of substrates rather than using high deposition temperatures and AlN buffer layer.…”

“…However, PEALD growth of GaN on Si usually associates with the issue of high impurities of oxygen and carbon in the deposited films, − especially high oxygen concentrations during the initial stage of growth . Oxygen, which is commonly present as a contaminant, is a donor in GaN, that can deteriorate the crystal quality of GaN.…”

From radical-enhanced to pure thermal ALD of gallium and aluminium nitrides

“…that the technology is in a nascent phase. As a matter of fact, the number of ALD GaN reports, focussed mostly on the material properties, is growing in the recent times 53,[89][90][91][92][93][94][95][96] . Some of the reported (and perceived) applications include TFTs [43][44] , sensors, and photodetectors [97][98][99] .…”