A process for the production of a layer of a semi-conducting ab compound by electrolytic deposition

摘要

In a process for the production of a layer of a semi-conducting AIIIBV compound by electrolytic decomposition, where AIII is an element in Group III of the Perodic Table and BV is an element in Group V, the compound is deposited from a solution containing the ions of the elements AIII and BV together with a complex forming agent, the pH being such that the complex of the nobler element is more stable than that of the less noble element, the potentials at which the elements are deposited from the complexes are similar and the hydrogen separation at the cathode is small at the impressed potentials. An electrolyte for depositing InSb comprises InCl3, SbCl3, NH4Cl, tartaric acid as a complexing agent, and gelatine for improving the surface quality of the deposited layer. The pH is adjusted to about 2.5 with concentrated NH3 solution and the electrolysis may be carried out at 3.5 volts. Other specified compounds which may be prepared similarly are InBi, InAs, GaSb, GaAs, AlSb and AlAs. A series of layers consisting of different AIIIBV compounds may be deposited. A doping can be carried out during the deposition. In apparatus for carrying out the process cathode 4 and anode 16 spaces are connected by an electrolyte bridge 12 having diaphragms 13 and 14. The cathode 4, which is held in a stopper 8, comprises a ferrite wafer and electrical contact is made with it through a graphite cushion 5 and a spring pressed copper contact 6. In measuring the cathode potential, a calomel electrode 10 is used. The cathode space contains the deposition electrolyte whereas the bridge and anode space contain an electrolyte such as KNO3 solution. Alternatively, the whole apparatus may contain the deposition electrolyte. The cell can be freed from dissolved H2 by the introduction of N2 before electrolysis is started. An admission pipe 17 and exhaust duct 18 are for this purpose. A magnetic stirrer is provided at 19.