Application of a new theoretical transport study to the assessment of the purity of ZnSe
Zinc selenide has been studied for a long time, mainly as a candidate for blue light electroluminescence. The main problem is to achieve a good control of the conductivity. Surprisingly, up to now, there have been few attempts to study the electrical properties of the material, in order to find the ultimate limits of the transport parameters and to determine the purity of the layers accurately. The authors have made a detailed analysis of the transport properties: the scattering mechanisms are discussed and the relevant ones are included in the Boltzmann transport equation, which is solved using two methods (variations and Rode's iterative method). The drift and Hall mobilities, as well as the Hall ratio are plotted against Hall factor at 300 K and 77 K, the compensation ratio (defined as Na-/Nd+) being used as a parameter. These results can be used a s tool for assessing the material quality, by deducing the compensation ratio at 300 K and 77 K from Hall measurements. The authors apply this to their growth results as well as to other results reported in the literature and they discuss the purity of the material obtained in MBE and MOVPE. The nature of the impurities is discussed from the influence of the growth parameters and it is assumed that group VII elements are the dominant donor species while group 1a elements are the main acceptors.