Photoluminescence studies in CuAlSe2 epilayers grown by low-pressure metalorganic chemical-vapor deposition

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Abstract
Low‐temperature photoluminescence (PL) spectra were investigated for CuAlSe2 epilayers grown on GaAs(001) substrates by means of low‐pressure metalorganic chemical‐vapor deposition. PL properties were studied with relation to metalorganic precursors used for the growth. High‐quality undoped epilayers exhibited PL peaks related to a free exciton (2.739 eV) and a bound exciton (2.677 eV). The other undoped epilayers exhibited PL bands at 2.3, 2.4, and 2.5 eV originating from donor‐acceptor (D‐A) pair recombinations. Some of them were found to have a common activation energy for the thermal quenching of 50±10 meV. The PL spectrum changed drastically by impurity doping. Intense green emissions at 2.51 and 2.43 eV were observed in Zn and Mg‐doped epilayers, respectively, which were interpreted as D‐A pair recombinations based on the dependencies of the PL spectra on excitation intensity, decay time, and temperature. The donor and the acceptor activation energies (ED and EA) were estimated to be 110 and 230 meV, respectively, for the Zn‐related D‐A pair emission at 2.51 eV. Similarly, ED and EA for CuAlSe2:Mg were estimated to be 140±10 and 270±10 meV, respectively. Furthermore, D‐A pair recombinations between 2.3 and 2.5 eV for CuAlSe2:I were studied. CuAlSe2 was proven to be a promising material for short‐wavelength visible‐light‐emitting devices.