Electro-optical device with inverted transparent substrate and method

Abstract

An electro-optical device with a transparent substrate is produced by epitaxially first growing the active device layers, followed by growth of the transparent substrate layer on an opaque wafer. The opaque wafer is subsequently removed. The active device layers have dopants with sufficiently low diffusivities that their electronic characteristics are not adversely affected by long exposure to elevated temperature during the growth of the transparent substrate layer. In a liquid phase epitaxy (LPE) method, a repeated temperature cycle technique is used where the temperature is repeatedly raised each time after cooling to provide a large cooling range for growing a sufficiently thick substrate layer or a series of device layers. In between growths and during the temperature heat-up periods, the device is stored within the LPE reactor. When a epitaxial layer is oxidizable, a non-oxidizable cap is temporarily grown on it in between growths and during the temperature heat up periods. The cap is subsequently removed by melting back at an elevated temperature just prior to the growth of a next layer. The technique may also be used for growing a transparent substrate which is lattice mismatched with the active deivce layers.