Wide-Gap p-Type Layered Oxychalcogenides AE₂CuInO₃Ch (AE: Alkaline Earth; Ch: Chalcogen): Unusually Low Residual Carrier Concentration and Green-to-Red Emission

Abstract

The absence of efficient green−yellow light emission in III-V group semiconductors, (Al,Ga,In)-(N,P,As), is a serious issue of inorganic solid-state light-emitting devices. A series of layered Cu-based oxychalcogenides, LaCuOCh (Ch = chalcogen), is known as wide-gap (E g = 2.4−3.1 eV) p-type semiconductors exhibiting high optoelectronic performance such as high hole mobilities and excitonic blue emission even at room temperature. However, they cannot reduce the residual carrier concentration similar to many oxide and chalcogenide semiconductors. In this paper, we demonstrate that layered oxychalcogenides, AE 2 CuInO 3 Ch (AE = Sr and Ba; Ch = S, Se, and Te), exhibit ptype semiconductor properties and green-to-red light emission. The room-temperature electronic conductivity (σ) of Sr 2 CuInO 3 Ch is significantly suppressed from 1.8 × 10 0 to 1.9 × 10 −4 S/cm by substituting Ch with Te to Ch with S. Exceptionally, Ba 2 CuInO 3 S exhibits a highly resistive state with σ = 1.9 × 10 −9 S/cm, originating from an unusually reduced residual hole concentration of ∼10 13 cm −3 , which is totally different from other Cu-based (oxy)chalcogenide semiconductors including LaCuOCh. First-principles defect calculations reveal that the source of holes is Cu vacancy, while In Cu antisite and S vacancy work as coexisting donor-type defects and compensate the generated holes, leading to the stable low carrier concentrations. Furthermore, AE 2 CuInO 3 Ch exhibit green, orange, and red emission owing to their direct-transition-type E g of 1.2−2.2 eV. Thus, AE 2 CuInO 3 Ch are new promising candidate semiconductors for a visible light source.