Stanford researchers have developed new ternary semiconducting compounds for optical device applications, as potential replacements for conventional materials like GaN, CIGS and ITO. These ternary compounds can be used to form the radiation absorption layer of a photovoltaic cell, the light emitting material of a light emitting device, the gain medium of a laser diode, the light absorbing layer of the photodetection device, the absorption medium of a modulator, a transparent electrode or a window layer.
These ternary semiconducting compounds having a stoichiometry of 1:1:1 and an element combination selected from the set of I-II-V, I-III-IV, II-II-IV, and I-I-VI; or having a stoichiometry of 3:1:2 and an element combination selected from the set of I-III-V; or having a stoichiometry of 2:1:1 and an element combination selected from the set of I-II-IV. For example, Li3AlN2 (band gap 4.4eV) and LiMgN (band gap 3.2eV) are particularly suitable for wide band gap applications such as LED in the blue to ultraviolet spectrum and transparent electrodes. NaZnAs, CaCuN, CaCuP, NaZnSb, CuZnP, NaZnP, and NaZnN having a direct band gap in the range of 0.8eV to 2.0eV are suitable for photovoltaic applications. The elements in these materials can be partially replaced by elements of the same group, in the one-by-one manner to maintain their insulating nature. For example, LiMgN can be tuned to be LiMg1-xZnxN. By tuning the materials, their band gap can be continuously changed to cover a broad light spectrum.
Most of these materials are theoretically predicated, while some such as Li3AlN2 have already been synthesized. Further development towards producing prototype devices is in progress.
Ternary semiconductor to replace binary compounds with similar band gaps can be formed by maintaining 8 or 18 total valence electrons.