Pressure dependence of energy gap of III–V and II–VI ternary semiconductors Dongguo Chen • N. M. Ravindra Received: 3 February 2012 / Accepted: 30 March 2012 / Published online: 19 April 2012 Ó Springer Science+Business Media, LLC 2012 Abstract A general expression for the pressure depen- dence of the energy gap of a series of group III–V and group II–VI ternary semiconductors have been derived based on Van Vechten’s dielectric theory. The results obtained are in good accord with the available experi- mental data. The trends in the variation of the pressure dependence of the energy gap with the nearest neighbor distance and Phillips ionicity are explored qualitatively. Introduction Semiconductor ternary compounds have been widely used because of the ability to tailor their optoelectronic prop- erties, in particular, the band gap, with composition. For instance, Al x Ga 1-x N has become a well-established mate- rial for UV light emitters and UV detectors due to the fact that its band gap covers a broad range [1] of wavelengths in the ultraviolet. ZnS x Se 1-x has been widely used for opto- electronic applications in blue–green spectral region [2] and CdS x Se 1-x plays an important role in semiconductor doped glasses [3]. Along with these applications, signifi- cant interests and efforts have been directed towards their fundamental material properties. One such example is the interest in pressure dependence of the band gaps of these ternary compound semiconductors. In general, there has been very little data on the pressure dependence of the energy gap of ternary compound semiconductors and even within the limited available experimental data, there is a significant variation. For example, the pressure coefficient of the band gap of Ga 0.5 In 0.5 P, reported by Hakki et al. [4] is 13 meV/kbar, in contrast with the 8.4 meV/kbar obtained by Chen et al. [5]. Thus, a theoretical approach is required to analyze the problem. In condensed matter physics, ab initio methods have been used to predict the pressure coefficients of the energy gap of some ternary compounds. However, possibly due to the approximations and assumptions made in these calcu- lations, the results are not always reliable. In general, ab initio calculations are complex and require significant efforts. Therefore, empirical approaches have been devel- oped to address some of these problems. The transition from binary compound semiconductors to ternary com- pound semiconductors requires the understanding of the bowing parameter [6]. Fundamentally, the bowing param- eter is the result of the deviation of the energy gap of the ternary compound from that of the alloy system comprising of the two binary compounds. Mathematically, the bowing parameter of a ternary compound AB x C 1x is expressed by the following equation: E g ðxÞ¼ xE AB g þ 1  x ð ÞE AC g  c ABC xð1  xÞ ð1Þ where, x is the composition in the compound AB x C 1x , E AB g and E AC g are the energy gaps of binary compounds AB and AC, respectively and c ABC is the bowing parameter. Hill [6] has ascribed the physical meaning of the bowing parameter to the nonlinear dependence of the crystal potential on the properties of the component ions and derived the following expression: c ABC ¼ Zer BC 4p 0 1 r B  1 r C   2 exp  1 2 sr BC   ð2Þ in which Z = Z B = Z C is the valence number of ions B and C, r B and r C are the covalent radii of B and C, D. Chen  N. M. Ravindra (&) Department of Physics, New Jersey Institute of Technology, Newark, NJ 07102, USA e-mail: nmravindra@gmail.com 123 J Mater Sci (2012) 47:5735–5742 DOI 10.1007/s10853-012-6464-5