A METHOD FOR CONTROLLING THE CRITICAL SUPERCOOLING IN LP
V.A.Mishurnyi, F.De Anda, A.Yu.Gorbachev. IICO - UASLP, Alvaro Obregon 64, San Luis
Potosi,78000, SLP. Mexico. Tel: (48) 250183, Fax: (48) 250198, e-mail:
It is known that GaSb is eroded strongly in the contact with Sb-rich liquid phases, used for the growth by LPE of such systems, as AlGaAsSb and InGaAsSb. As a result of that processes the interfaces between different epitaxial layers are irregular and wavy. Obviously, in order to fabricate high quality devices, it is necessary to depress that erosion. It can be done, in particular, by increasing the initial supercooling of the liquid phase before its contact with the substrate. In the AlGaAsSb case it is difficult to use this method due to a very low critical supercooling DTcr. of the quaternary Al-Ga-As-Sb liquid with Sb as a solvent. It is known, that the critical seed radius and consequently DTcr. depend on the specific surface energy between liquid and solid phases. So it is possible to control DTcr by changing the liquid phase composition. Naturally it is necessary to vary that composition with minimal influence on the solid phase composition. This can be achieved by the introduction in the liquid phase of any elements with low segregation coefficient. In the present work DTcr was studied by direct visual observation during slowly heating and cooling the liquid phases. It is shown, that the addition of Indium to Al-Ga-As-Sb and Antimony to In-P liquid phases increase their DTcr from 4 to 100C in the first case and from 10 to160C in the second case. So it is suggested and developed a new method to control DTcr which can be useful for the LPE processes.