Abstract
Gallium oxide (Ga2O3) thin films of various thicknesses were grown on sapphire (0001) substrates by metal organic chemical vapor deposition (MOCVD) using trimethylgallium (TMGa), high purity deionized water, and silane (SiH4) as gallium, oxygen, and silicon precursors, respectively. N2 was used as carrier gas. Hall measurements revealed that films grown with a lower VI/III ratio had a dominant p-type conduction with room temperature mobilities up to 7 cm2/Vs and carrier concentrations up to ~1020 cm−3 for thinner layers. High resolution transmission electron microscopy suggested that the layers were mainly κ phase. Microstrip field-effect transistors (FETs) were fabricated using 2D p-type Ga2O3:Si, channels. They achieved a maximum drain current of 2.19 mA and an on/off ratio as high as ~108. A phenomenological model for the p-type conduction was also presented. As the first demonstration of a p-type Ga2O3, this work represents a significant advance which is state of the art, which would allow the fabrication of p-n junction based devices which could be smaller/thinner and bring both cost (more devices/wafer and less growth time) and operating speed (due to miniaturization) advantages. Moreover, the first scaling down to 2D device channels opens the prospect of faster devices and improved heat evacuation.
Highlights
Gallium oxide (Ga2 O3 ) with an ultra-wide bandgap (UWBG) of ~4.9 eV has emerged as a generation semiconductor material for high power electronic devices.This is in great part due to its high breakdown electric field (~8 MV/cm), which largely surpasses that of competing materials systems such as SiC or GaN
The emergence of n-type doping capacity and single crystal Ga2 O3 substrates has allowed the development of various unipolar electronic devices including metal oxide semiconductor field effect transistors (MOSFETs), Schottky diodes, and metal semiconductor field effect transistors (MESFET), which have been demonstrated based on high quality homo-epitaxial growth [1,2,3]
We showed that κ-Ga2 O3 could be stabilized in heteroepitaxial growth on sapphire (0001) substrates by metal organic chemical vapor deposition (MOCVD) [4,5,6,7,8,9,10,11,12]
Summary
Gallium oxide (Ga2 O3 ) with an ultra-wide bandgap (UWBG) of ~4.9 eV has emerged as a generation semiconductor material for high power electronic devices. This is in great part due to its high breakdown electric field (~8 MV/cm), which largely surpasses that of competing materials systems such as SiC or GaN. A major drawback of β-Ga2 O3 until recently, has been lack of a method to obtain p-type conduction; this is a key limitation for its adoption in a whole range of semiconductor device applications.
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