Quasi‐Single Crystalline Cuprous Oxide Wafers via Stress‐Assisted Thermal Oxidation for Optoelectronic Devices

Abstract P‐type semiconductor cuprous oxide (Cu₂O) offers promising optoelectronic applications such as solar cells and photodetectors owing to its considerable absorption coefficients and high carrier mobility. However, polycrystalline Cu₂O films with low carrier mobility resulting from excessive grain boundaries and structure disorder fail to meet the demands for these optoelectronic applications. Here a stress‐assisted thermal oxidation method to fabricate p‐type <110>‐textured quasi‐single crystalline Cu₂O (c‐Cu₂O) wafers with centimeter‐scale grains is developed. It is found that strain energy induced by thermal contact stress plays a critical role in crystal growth. The resultant <110>‐textured quasi‐single c‐Cu₂O wafers exhibit excellent crystallinity with rocking curve having a low full width at half maximum of 0.022°, a low defect density of 2 × 10¹¹ cm⁻³, a high mobility exceeding 100 cm² V⁻¹ s⁻¹, and a long minority lifetime of 98.5 µs. Such quasi‐single c‐Cu₂O wafers lead to efficient solar cells with an open‐circuit voltage of 0.95 V and highly responsive photodetectors with superior cycling stability. These results indicate not only the advancement of fabricating high‐quality Cu₂O wafers upon controllable methodology but also the promising optoelectronic applications using p‐type metal oxide semiconductors.