The p-HgCr₂Se₄/n-CdIn₂S₄ heterojunction was prepared by the method of closed-tube vapour phase epitaxial growth using 1.5 mol%Ag doped HgCr₂Se₄ single crystal as the substrate, CdIn₂S₄ powder as the source material and I₂ as a transport agent.
The constituents containing in the HgCr₂Se₄-CdIn₂S₄ heterojunction varied abruptly at the interface within the resolving power of EPMA; however, Hg and Cd only are mutually replaced with one another to a certain depth in the direction from the junction interface toward the HgCr₂Se₄ interior and the inside of the CdIn₂S₄ epitaxial layer. Although these mutual replacement depths do not depend on the substrate temperature and the temperature difference between the growth and the higher temperature ends, they depend strongly on I₂ concentration. To be more precise, the smaller I₂ concentration, the thinner are the mutual replacement regions. The existence of the mutual replacement regions was confirmed by measurement of the photovoltaic property.
The long wavelength edge of the photoresponse for the p-HgCr₂Se₄/n-CdIn₂S₄ heterojuction diodes devoid of this mutual replacement regions showed a red shift, indicating that the red shift is in good agreement with the temperature dependence of the optical absorption edge of HgCr₂Se₄.