Cadmium telluride light emitting diode

Cadmium telluride has been synthesized from the purified elements. This process, when conducted under "Semi-white" room conditions in inert atmosphere has not introduced cation impurities. A Bridgman growth technique has yielded single crystals 10 mm diameter up to 50 mm long. Undoped crystals are weakly p-type and reproducible. Heavily doped n-type crystals have also been grown with less reproducibility. Heavily doped n-type crystals are low resistivity, 1 to 10 ohm-centimeter. A vapor-phase growth technique has yielded single crystals up to several mm³in volume. The undoped crystals are weakly p-type. Alloy pn junctions showing both photovoltage and photomodulation have been fabricated on weakly p-type wafers. Some units have demonstrated a zener type of breakdown in the reverse direction. The maximum voltage thus observed is about 25 v. Alloy pn junctions showing both photovoltage and photomodulation have been fabricated from 0.05 percent indium doped single crystal cadmium telluride. The material has a resistivity of about one ohm-centimeter. Forward characteristics show a knee at 200 or 300 millivolts. The reverse breakdown is nearly zener type at 20 volts.