Hot-wall-epitaxy growth and electrical/optical characterization of epitaxial BaAl2S4/GaAs layers

• The epitaxial layer growth was first achieved by the hot-wall-epitaxy method.
• Characteristic property was found by means of DCXD, Hall effect, and PC measurements.
• The band to band transition was extracted out through PC spectroscopy.
• The band gap energy was compared with the optical absorption and PC measurements.

The BaAl2S4 layers, which were identified to be a cubic structure in space group Pa3, were grown using the hot wall epitaxy method attached with the reservoir tail. Also, the coincidence lattice mismatch of the grown layers was shown to be −2.52% due to the influence of the compressive strain. The Hall effect measurement showed the different temperature-dependent decrease of mobility at a temperature above 100 K. One was T−1/2 at the temperature range of 100180 K. The mobility decreased in proportion to T1 at a low temperature range of T<100 K. Three PC peaks obtained from the photocurrent (PC) spectra were corresponding to band-to-band transitions, which were observed over the temperature range. These PC peaks were caused by the transition of electrons from the three valence band states in order of increasing energy to the conduction band states, respectively. By analyzing absorption and PC results, the band gap variation has been compared and matched well with Eg(T)=Eg(0)−7.556×10−4T2/(T+523), where Eg(0) is estimated to be 4.0596, 4.1053, and 4.1094 eV.