Low pressure chemical vapor deposition of β-Ga2O3 thin films: Dependence on growth parameters

Zixuan Feng,Md Rezaul Karim,Hongping Zhao

doi:10.1063/1.5054713

Zixuan Feng, Md Rezaul Karim + Show 1 more

Open Access

https://doi.org/10.1063/1.5054713

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Journal: APL materials	Publication Date: Dec 14, 2018
Citations: 42	License type: cc-by

Affiliation: The Ohio State University

Abstract

Low pressure chemical vapor deposition (LPCVD) has been used to produce high quality β-Ga2O3 materials with controllable n-type doping. In this work, we focus on the studies of key LPCVD growth parameters for β-Ga2O3 thin films, including oxygen/carrier gas flow rates, growth temperature, pressure, and the substrate to Ga crucible distance. These growth parameters play important roles during the LPCVD β-Ga2O3 growth and determine the thin film growth rate, n-type dopant incorporation, and electron mobilities. The dependence of the growth parameters on LPCVD of β-Ga2O3 was carried out on both conventional c-plane sapphire and 6 degree off-axis (toward ⟨11-20⟩ direction) sapphire substrates. To better understand the precursor transport and gas phase reaction process during the LPCVD growth, a numerical model for evaluating the growth rate was developed by using a finite element method and taking into account the gas flow rate, chamber pressure, and chamber geometry. The results from this work can provide guidance for the optimization of the LPCVD growth of β-Ga2O3 with targeted growth rate, surface morphology, doping concentration, and mobility. In addition, β-Ga2O3 grown on off-axis c-sapphire substrates features with faster growth rates with higher electron mobilities within a wide growth window.

Highlights

Another key advantage of β-Ga2O3 as compared to the existing wide bandgap semiconductors such as GaN and SiC is its availability of bulk single crystals synthesized by low cost and scalable melt-based growth methods including the floating zone method (FZ),2,9–11 Czochralski (CZ) method,12–14 and edgedefined film-fed growth (EFG) method
The growth of β-Ga2O3 thin films has been conducted by different growth techniques including molecular beam epitaxy (MBE),17–24 halide vapor phase epitaxy (HVPE),25–28 metalorganic chemical vapor deposition (MOCVD),29–34 LPCVD,8,35–40 and pulsed laser deposition (PLD)
The room temperature electron mobility of 100-110 cm2/V s has been achieved in LPCVD grown homoepitaxial and heteroepitaxial β-Ga2O3 films

Summary

Introduction

The large bandgap corresponding to a transition wavelength at ∼250 nm enables β-Ga2O3 for optoelectronic devices operating in the deep ultraviolet (DUV) wavelength region, e.g., solar blind photodetectors.8 Another key advantage of β-Ga2O3 as compared to the existing wide bandgap semiconductors such as GaN and SiC is its availability of bulk single crystals synthesized by low cost and scalable melt-based growth methods including the floating zone method (FZ),2,9–11 Czochralski (CZ) method,12–14 and edgedefined film-fed growth (EFG) method.15,16 Currently, the assynthesized β-Ga2O3 substrates exhibit n-type conductivity scitation.org/journal/apm with a doping concentration in the order of 1-9 × 1017 cm−3 (Nd − Na). The β-Ga2O3 films grown on the off-axis sapphire substrates still show enhanced mobilities under the investigated growth conditions.

Results

Conclusion