Laser Processing of Wide-Gap II-VI Compounds for Improved Conductivity Control

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A long-standing problem for wide-band-gap semiconductors (band gap greater than about 2 eV) is that of obtaining good bipolar conductivity, with resultant problems of obtaining good (efficient) p-n- cunctions. This problem has been particularly severe in the II-VI materials, which otherwise have a umber of desirable properties. Recent work has shown that the basic difficulty resides in a poor solubility of shallow dopants. Consequently, non-equilibrium impurity incorporation is generally required. We propose to work with laser processing, in view of its very rapid thermal quenching and its photolytic doping capabilities. It will be checked whether such processing can give adequate conductivity with use of just a single (primary) dopant, or whether a newly suggested procedure , joint incorporation of both such a primary dopant and a (mobile) compensating species, with subsequent removal of the latter, will be required . We plan to focus on ZnSe, but with some work probably also on CdS, and obtain well - conducting p-type, reproducible. This has not been previously achieved. Good p-type would lead to good p-n junctions, since good n-type is available, and resultant devices, such as light emitting diodes and diode lasers in the green and higher spectral ranges, and better solar cells.