Formation of HgCdTe by Electrochemical Atomic Layer Epitaxy (EC-ALE)

Formation of Hg(1-x)CdxTe (MCT), thin films by electrochemical atomic layer epitaxy (EC-ALE) is reported. EC-ALE is the electrochemical analog of atomic layer epitaxy (ALE) and atomic layer deposition (ALD), and thus involves the growth of films an atomic layer at a time, using surface limited reactions. Underpotential deposition (UPD) is a type of electrochemical surface limited reaction, used in the present study for the formation of good quality MCT deposits using EC- ALE. The MCT films were formed using an automated electrochemical flow cell deposition system, so that potentials and solutions could be exchanged as desired, without loss of potential control or exposure of the deposit to the ambient. Deposits were characterized using X-ray diffraction (XRD), electron probe microanalysis (EPMA) and reflection absorption Fourier transform Infrared spectroscopy (FTIR). The as-deposited films showed a strong (111) preferred growth orientation. The EPMA results indicated that the Cd rich film had an alloy composition of Hg0.5Cd0.5Te and the Hg rich film had a composition of Hg0.8Cd0.2Te. The bandgaps of the Hg0.5Cd0.5Te and Hg0.8Cd0.2Te deposits were measured to be 0.70 eV and 0.36 eV respectively.