Time of flight mass spectroscopy of recoiled ions studies of surface kinetics and growth peculiarities during gas source molecular beam epitaxy of GaN

Abstract

High growth rate GaN thin films were successfully grown by gas source molecular beam epitaxy and studied in situ by time of flight mass spectroscopy of recoiled ions (TOF-MSRI) and reflection high energy electron diffraction (RHEED). We show that TOF-MSRI allows for in situ monitoring and control of sapphire surface chemistry and its nitridation. In the latter case, TOF-MSRI is more sensitive to the surface changes during nitridation than RHEED. Using both RHEED and TOF-MSRI, growth of low-temperature GaN buffer layers was monitored, and their recrystallization and island-like nature were demonstrated. A model describing the probable growth mechanism for gas source molecular beam epitaxy of GaN is suggested. The model explains both the chemical dissociation of ammonia at low temperature and the origin of Ga to N TOF-MSRI peak ratio changes for various Ga and ammonia fluxes. High-resolution transmission electron microscopy studies confirm that GaN films grown with a buffer layer have excellent structural quality without any evidence of interfacial defects. Those without a buffer layer are highly defective.

Morphology of GaN Surfaces and GaN/(Al,Ga)N Interfaces Grown on 6H-SiC(0001) by Reactive Molecular Beam Epitaxy

“…While metalorganic chemical vapor deposition (MOCVD) routinely achieves atomically smooth GaN surfaces and GaN/(Al,Ga)N interfaces, there has been hardly any report demonstrating the same level of growth control for structures fabricated by molecular beam epitaxy (MBE) [1,2]. For GaN-based heterostructures, this issue becomes particularly important due to the presence of large polarization-induced fields.…”

In situ surface composition and structure of InGaN and GaN thin films by time-of-flight mass spectroscopy of recoiled ions

“…In particular, ISS/ DRS is similar to the widely used ex situ secondary ion mass spectroscopy, but differs from it in that it is tuned to detect much higher energy recoiled and scattered ions. 6,7 In this article, we will briefly describe the TOF-MSRI technique and present our results from GaN and InGaN films grown by MBE with ammonia or ECR-N 2 plasma as a nitrogen source. The glancing geometry coupled with time-of-flight ͑TOF͒ measurements of these high-energy recoils permit surface composition determination ͑crystalline or amorphous͒ during deposition at pressures up to 10 Ϫ2 Torr.…”

Growth of GaN from elemental Gallium and Ammonia via Modified Sandwich Growth Technique

“…[80]. In a first step, and in order to form theGaN molecule, the reaction barrier must be reduced either by an increase in the energy of the reactant molecules or thorough a feasible chemical reaction path.…”