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Gallium oxide (Ga₂O₃) is a highly promising ultrawide‐bandgap semiconductor for power electronics that emerged about a decade ago. Epitaxial growth Ga₂O₃at the small scale is demonstrated. In order to develop scalable manufacturing of high‐performance epitaxial structures, in‐depth understanding of the fundamental growth processes, control parameters, and mechanism is imperative. This review discusses the recent progress in epitaxial growth of β‐Ga₂O₃films and highlights challenges in obtaining high growth rate, low defects, and high carrier mobilities. Compared with the other epitaxy methods, metal–organic chemical vapor deposition (MOCVD) offers a wider growth window and precursor selection option, to minimize the tradeoff between crystal quality and growth rate. Growth rate is inversely proportional to temperature, within a certain temperature window, because of the unavoidable premature gas‐phase reactions and desorption of the highly volatile gallium suboxide (Ga₂O) at elevated temperatures. Growth defects, background impurity incorporation, and carrier mobilities can be affected by the choice of MOCVD precursors, nucleation, and adsorption/desorption/diffusion of adatoms on substrate surfaces of different orientations, including the effect of growing on cleavage and noncleavage planes. This review summarizes the current status of the epitaxial growth of β‐Ga₂O₃and analyzes the major factors that enhance mobility and reduce background doping concentration. The insights gained help advance the manufacturability of device‐grade epitaxial thin films.

III–V semiconductor‐based photodiodes with graphene incorporated have been studied in recent years due to the attractive optoelectronic properties of graphene, including optical transparency and enhanced photoresponsivity. The photoresponsivity can be further improved by converting the semiconductor surface into a 3D antireflection (AR) structure. However, difficulties in transferring graphene on top of structured surfaces degrade the interfacial quality and limit their photoresponsivity. Herein, a high‐performance GaAs photodiode structure with self‐embedded graphene quantum dot (GQD) and simultaneously formed periodic AR 3D surface texturing is reported, all produced by a one‐step wet etching process in a solution of hydrogen fluoride (HF) and potassium permanganate (KMnO₄) using graphene as a transparent mask. Compared with the planar counterpart without graphene, the photodiodes demonstrated here show an enhancement of photocurrent by 22 times, photoresponsivity by 25 times, and normalized photocurrent to dark current ratio by approximately two orders of magnitude. The improved photoresponsivity of 9.31 mA W⁻¹is attributed to the increased absorption from AR texturing and the enhanced heterointerface carrier transfer from GQDs to GaAs. This simple, clean yet effective method enables the monolithic incorporation of graphene and graphene‐derived materials on 3D semiconductor structures for applications across a wide range of wavelengths.