Optische Untersuchungen über die Halbleitereigenschaften von As- und Zn3As2- Schichten

One of the fundamental constants of semiconductors is the energy gap [Delta]E between the top of the valence band and the bottom of the conduction band. For its determination electrical and optical methods are equally convenient. In this paper the authors report on optical measurements of [Delta]E on thin layers of As and some Zn-As-alloys. X-ray- and optical investigations on these layers, produced in high vacuum, confirm their crystalline structure, their homogeneity and in the case of Zn3As2 the formation of the compound Zn3As2. The optical oonstants of As and Zn3As2 are calculated by means of the Maxwell-theory from reflection- and transmission-curves in the spectral region from 0,5 to 2,7 [my]. Assuming the threshold wavelength belonging to an absorption constant K = 1 mm^-1 the authors obtain for As [lambda]g = 1,16 [my] corresponding to [Delta]E = 1,07 eV and for Zn3As2 [lambda]g = 2,44 [my], which corresponds to 0,51 eV. The experimental results are discussed in comparison with previous electrical and optical measurements on the amorphous As.