MOCVD growth of high purity Ga2O3 epitaxial films using trimethylgallium precursor

Abstract

We report on the growth of β-Ga2O3 thin films using trimethylgallium (TMGa) as a source for gallium and pure O2 for oxidation. The growth rate of the films was found to linearly increase with the increase in the molar flow rate of TMGa and reach as high as ∼6 μm/h at a flow rate of 580 μmol/min. High purity, lightly Si-doped homoepitaxial β-Ga2O3 films with a good surface morphology, a record low temperature electron mobility exceeding 23 000 cm2/V s at 32 K, and an acceptor concentration of 2 × 1013 cm−3 were realized, showing an excellent purity film. Films with room temperature (RT) electron mobilities ranging from 71 cm2/V s to 138 cm2/V s with the corresponding free carrier densities between ∼1.1 × 1019 cm−3 and ∼1.5 × 1016 were demonstrated. For layers with the doping concentration in the range of high-1017 and low-1018 cm−3, the RT electron mobility values were consistently more than 100 cm2/V s, suggesting that TMGa is suitable to grow channel layers for lateral devices, such as field effect transistors. The results demonstrate excellent purity of the films produced and confirm the suitability of the TMGa precursor for the growth of device quality β-Ga2O3 films at a fast growth rate, meeting the demands for commercializing Ga2O3-based high voltage power devices by metalorganic chemical vapor deposition.

Thermal Conductivity of β-Phase Ga2O3 and (AlxGa1–x)2O3 Heteroepitaxial Thin Films

“…By using N 2 O as an oxygen precursor, the background doping in the films can be reduced to ∼10 14 cm –3 . By reducing the acceptor densities to 2 × 10 13 cm –3 , a record high low temperature hall mobility of 23,000 cm 2 /V s has been achieved . The combination of high-room temperature and low-temperature mobilities confirms the high quality of MOVPE-grown β-Ga 2 O 3 thin films.…”

Role of carbon and hydrogen in limiting $n$-type doping of monoclinic (Al$_x$Ga$_{1-x}$)$_2$O$_3$

“…C O -H, finally, was found to act as an acceptor over the entire range of alloy compositions, behaving very similarly to a N O substitutional impurity and explaining experimental observations of carbon-related compensation in Ga 2 O 3 grown by MOCVD. [33,34] Our findings indicate that the presence of hydrogen or carbon may interfere with controlled low-level Si doping in (Al x Ga 1−x ) 2 O 3 alloys, and our detailed results can be used to devise growth or processing conditions to avoid this.…”

“…We propose that the C O -H complexes may have a distinct impact on MOCVD-grown Ga 2 O 3 . Seryogin et al [33] grew Ga 2 O 3 using a trimethylgallium (TMGa) precursor, which is known to potentially lead to increased C incorporation. They found that films grown with a lower O 2 /TMGa ratio were significantly more resistive and also contained significantly more carbon.…”

“…C O will incorporate only under relatively cation-rich (oxygen-poor) conditions; we find that C O -H complexes can actually incorporate more easily, explaining experimental observations of carbon-related compensation in Ga 2 O 3 grown by MOCVD. [33,34] The paper is organized as follows. In Sec.…”

Wide Bandgap Vertical kV-Class β-Ga₂O₃/GaN Heterojunction p-n Power Diodes With Mesa Edge Termination

“…MOCVD is capable of controlling the doping densities up to ~10 19 cm -3 with low dislo-Dinusha Herath Mudiyanselage, Dawei Wang, and Houqiang Fu are with Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011 USA (e-mail: houqiang@iastate.edu). cation densities, providing high-quality epitaxial layers [10,11]. Recently, β-Ga2O3 power devices have been demonstrated with encouraging performance such as high breakdown voltages, high critical electric fields, high currents, and excellent thermal stability [12][13][14][15][16][17][18].…”