Simultaneous control of the composition and the stoichiometry for a multinary new solid solution semiconductor

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Attention is recently paid to the new materials for tunable laser diode, lasing at about 3.5mum. The laser diodes are expected as the light source for optical communications in the next generation. The quarternary (Pb_<1-x>Cd_x) (S_<1-z>Se_z)_<1+y> are best suited to the above purposes. In this study, a new method for simultaneously controlling the composition x,z and the deviation y from stoichiometry was proposed for the quarternay solid solution. That is, the activity of sulfur(Ps_2), selenium(Pse_2) and CdS_<1-z>Se_z(a_<cds1-z'sez'>) were controlled independently in the heat-treatment process of the solid solution by providing two reservoir chambers in the heat-treatment tube. They are the mixing reservoir of sulfur and selenium and a CdS reservoir. As a result, it was found that the composition x and z of the solid solution is seriously effected by a CdS reservoir(a_<cds1-z'sez'>) and the mole ratio of S and Se in the mixing reservoir, respectively. The deviation y from stoichiometry could also be controlled simultaneously by regulating the sum of chalcogen partial pressures (Ps_2+Pse_2), keeping a_<cds1-z'sez'> and the mole ratio of sulfur and selenium in the mixing reservoir to a specific value corresponding to the target composition x and z. Based on this principle, the diagrams of P(Ps_2+pse_2)-T(heat-treatment temperature)-y(deviation from stoichiometry) was obtained successfully for this quarternary solid solution.