The Secretary of State for Defence in Her Britannic Majesty's Government

Secretary of the State for Defence in Her Majesty's Government of the

Stuart J Irvine

John B Mullin

Jean Giess

A method of growing an epitaxial crystalline layer on a substrate which comprises the steps of

Method of growing crystalline layers by vapor phase epitaxy

A layer of Cd.sub.x Hg.sub.1-x Te is grown on the surface of a substrate by decomposing alkyls of cadmium and telluride in a mercury atmosphere. The substrate is placed in a vessel containing a mercury bath with the vessel and bath at a suitable pressure and a temperature below the alkyl decomposition temperature. Hydrogen is passed through bubblers separately containing alkyls of cadmium, telluride and, if required, a dopant into the vessel. The substrate is independently heated above the temperature of the vessel so that the alkyls decompose on the substrate. The substrate may be CdTe, a II-VI compound or mixed II-VI alloy. The alkyls may be dimethyl cadmium, diethyl cadmium, dipropyl cadmium, dimethyl telluride, diethyl telluride, dipropyl telluride, dibutyl telluride etc., or hydrogen substituted tellurium alkyls such as hydrogen ethyl telluride etc.

Manufacture of cadmium mercury telluride

A layer of Cd.sub.x Hg.sub.1-x Te is grown on a substrate by growing layers of HgTe t.sub.1 thick, and CdTe t.sub.2 thick alternately. The thicknesses t.sub.1 and t.sub.2 combined are less than 0.5 .mu.m so that interdiffusion occurs during growth to give a single layer of Cd.sub.x Hg.sub.1-x Te. The HgTe layers are grown by flowing a Te alkyl into a vessel containing the substrate and filled with an Hg atmosphere by an Hg bath. The CdTe layers are grown by flowing of Cd alkyl into the vessel where it combines preferentially with the Te on the substrate. Varying the ratio of t.sub.1 to t.sub.2 varies the value of x. Dopants such as alkyls or hydrides of Al, Ga, As and P, or Si, Ge, As and P respectively may be introduced to dope the growing layer.

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Malvern, United Kingdom

Stuart J Irvine