Transport Properties and Finite Size Effects in \u03b2-Ga2O3 Thin Films

Robin Ahrling,Günter Wagner,Johannes Boy,Martin Handwerg,Olivio Chiatti,Zbigniew Galazka,Saskia F Fischer,Rüdiger Mitdank

doi:10.1038/s41598-019-49238-2

Abstract

Thin films of the wide band gap semiconductor β-Ga2O3 have a high potential for applications in transparent electronics and high power devices. However, the role of interfaces remains to be explored. Here, we report on fundamental limits of transport properties in thin films. The conductivities, Hall densities and mobilities in thin homoepitaxially MOVPE grown (100)-orientated β-Ga2O3 films were measured as a function of temperature and film thickness. At room temperature, the electron mobilities ((115 ± 10) cm2/Vs) in thicker films (>150 nm) are comparable to the best of bulk. However, the mobility is strongly reduced by more than two orders of magnitude with decreasing film thickness ((5.5 ± 0.5) cm2/Vs for a 28 nm thin film). We find that the commonly applied classical Fuchs-Sondheimer model does not explain sufficiently the contribution of electron scattering at the film surfaces. Instead, by applying an electron wave model by Bergmann, a contribution to the mobility suppression due to the large de Broglie wavelength in β-Ga2O3 is proposed as a limiting quantum mechanical size effect.

Highlights

Thin films of the wide band gap semiconductor β-Ga2O3 have a high potential for applications in transparent electronics and high power devices
With the progress made in the production of homoepitaxial β-Ga2O3 thin films of high quality[16], they havVes a promising prospect for potential use in devices
Van-der-Pauw and Hall measurements were taken on the films in a temperature range from 30 K to 300 K for film thicknesses between 28 nm to 225 nm to determine conductivity, Hall density and mobility

Summary

Introduction

Thin films of the wide band gap semiconductor β-Ga2O3 have a high potential for applications in transparent electronics and high power devices. The conductivities, Hall densities and mobilities in thin homoepitaxially MOVPE grown (100)-orientated β-Ga2O3 films were measured as a function of temperature and film thickness. By applying an electron wave model by Bergmann, a contribution to the mobility suppression due to the large de Broglie wavelength in β-Ga2O3 is proposed as a limiting quantum mechanical size effect. Various temperature-dependent measurements of electrical parameters on bulk single-crystals, typically grown by the Czochralski-method, have been done before, with the highest mobilities measured in comparable bulk material (Hall densities of about some 1017 cm−3) so far being 152 cm[2 15]. A fundamental limit due to finite size effects[18], namely the interaction of electron waves with the film boundaries, is explored

Methods

Results

Conclusion