Discovery of a Robust <i>P</i>‐Type Ultrawide Bandgap Oxide Semiconductor: LiGa<sub>5</sub>O<sub>8</sub>
Kaitian Zhang, Vijay Gopal Thirupakuzi Vangipuram, Hsien‐Lien Huang, Jinwoo Hwang, Hongping Zhao
Abstract
Abstract LiGa 5 O 8 , an ultrawide bandgap semiconductor, is discovered to exhibit p ‐type conductivity at room temperature, making it the widest bandgap p ‐type oxide semiconductor known to date. Utilizing a mist–chemical vapor deposition (M–CVD) technique, successful growth of p ‐type LiGa 5 O 8 thin films on c ‐plane sapphire and GaN‐on‐sapphire substrates is achieved. Characterization through X‐ray diffraction and cross‐sectional scanning transmission electron microscopy (STEM) confirms the spinel cubic crystal structure of LiGa 5 O 8 . Comprehensive investigations into the effects of growth conditions on surface morphology, material composition, and p ‐type charge carrier transport are conducted. As‐grown LiGa 5 O 8 thin films exhibit a broad range of hole concentrations, ranging from 10 15 cm −3 to 10 18 cm −3 , depending on growth conditions. Elemental compositions of Li, Ga, and O are extracted using X‐ray photoemission spectroscopy (XPS). Both Li‐poor and Li‐rich LiGa 5 O 8 films demonstrate p ‐type conductivity. Optical absorption measurements reveal the bandgap of LiGa 5 O 8 films to be ≈5.36 eV. Additionally, temperature‐dependent Hall measurements of the p ‐type LiGa 5 O 8 thin films show robust p ‐conductivity down to 150 K. Results from this study promise the advancement of future power electronics based on ultrawide bandgap Ga 2 O 3 and related semiconductor material systems.