Freestanding Crystalline β-Ga₂O₃ Flexible Membrane Obtained via Lattice Epitaxy Engineering for High-Performance Optoelectronic Device

Abstract

Wearable and flexible β-Ga2O3-based semiconductor devices have attracted considerable attention, due to their outstanding performance and potential application in real-time optoelectronic monitoring and sensing. However, the unavailability of high-quality crystalline and flexible β-Ga2O3 membranes limits the fabrication of relevant devices. Here, through lattice epitaxy engineering together with the freestanding method, we demonstrate the preparation of a robust bending-resistant and crystalline β-Ga2O3 (−201) membrane. Based on this, we fabricate a flexible β-Ga2O3 photodetector device that shows comparable performance in photocurrent responsivity and spectral selectivity to conventional rigid β-Ga2O3 film-based devices. Moreover, based on the transferred β-Ga2O3 membrane on a silicon wafer, the PEDOT:PSS/β-Ga2O3 p–n heterojunction device with self-powered characteristic was constructed, further demonstrating its superior heterogeneous integration ability with other functional materials. Our results not only demonstrate the feasibility of obtaining a high-quality crystalline and flexible β-Ga2O3 membrane for an integrated device but also provide a pathway to realize flexible optical and electronic applications for other semiconducting materials.

Ultrasensitive Self-Powered Flexible Crystalline β-Ga2O3-Based Photodetector Obtained through Lattice Symmetry and Band Alignment Engineering

“…By fitting the response data, the response time τ r and decay time τ d of the flexible PD were determined to be 1.16 and 0.95 s, respectively. This response under zero bias is much better than that of flexible Ga 2 O 3 PD even under 10 V (τ r = 1.63 s, τ d = 1.65 s), indicating that the construction of flexible β-Ga 2 O 3 /NiO heterojunction indeed promotes the optoelectronic properties of the device. Actually, besides the response speed, the photo-to-dark ratios and response capacity of the flexible β-Ga 2 O 3 /NiO PD is also superior than that of flexible Ga 2 O 3 PD (Figure S8).…”

“…Previously, by taking the lattice symmetry and freestanding method, we successfully obtained high-quality flexible crystalline β-Ga 2 O 3 membranes. The small lattice mismatch in the β-Ga 2 O 3 /La 0.7 Sr 0.3 MnO 3 (LSMO)/SrTiO 3 (STO) (111) heterostructure ensures the high-quality crystalline of β-Ga 2 O 3 membranes . Moreover, for semiconductor heterostructures, it is well-known that there are three typical types of energy band alignment structures that can be used to design PDs, as depicted in Figure a. − For type-I and type-III band alignments, the straddling or broken band gap structure prevents the diffusion of carriers along the heterojunction, thus prompting these heterojunctions suitable for fabricating light emission or high-power devices. , While for type-II energy band alignment structure, the decent band edge effectively separates electron–holes pairs and facilitates carrier transport. , Based on these, we know that if we can select a p -type semiconductor target material that can achieve type-II energy band alignment with n -type β-Ga 2 O 3 ; then, we can fabricate the high-quality crystalline β-Ga 2 O 3 /target material/LSMO/STO heterojunction.…”