Impact on structural, optical and electrical properties of CuCl by incorporation of Zn for n-type doping

Abstract

γ-CuCl is a wide-band gap (Eg = 3.395eV at 4 K) , direct band gap, semiconductor material with a cubic zincblende lattice structure. A very large exciton binding energy (190 meV), assures efficient exciton-based emission at room temperature. Its lattice constant, means that the lattice mismatch to Si (aSi=0.543 nm) is <0.5%. γ-CuCl on Si—the growth of a wide-band gap, direct band gap, optoelectronics material on silicon substrate is a novel material system, with compatibility to current Si-based electronic/optoelectronics technologies. Both n-type and p-type CuCl will be required for development of homojunction light-emitting diodes (LEDs). The authors report on the impact of incorporation of Zn for n-type doping of CuCl by co-evaporation of CuCl and ZnCl2. Polycrystalline Zn-doped γ-CuCl thin films are grown on Si (1 1 1), Si (1 0 0), and glass substrates by physical vapour deposition. X-ray diffraction (XRD) studies confirm that this n-doped CuCl has a cubic zincblende structure with a preferred (1 1 1) orientation. Several excitonic bands are evident in low-temperature photoluminescence (PL) measurements such as the Z3 free exciton at ∼388 nm; I1-bound exciton at ∼392 nm and M free biexciton at ∼393 nm. Cathodoluminescence (CL) and PL reveal a strong room temperature Z3 excitonic emission at ∼385 nm. Electrical measurements indicate n-type conductivity with resistivity ∼34 Ωcm.