Techniques for Melt-Growth of Luminescent Semiconductor Crystals under Pressure

Abstract

Wide-bandgap III-V and II-VI binary semiconductor crystals can be grown from the melt by a variety of methods, all requiring pressure. The necessary apparatus, from the simple to the sophisticated, has been investigated. Methods using resistance or rf heating, unsupported or supported ampoules of several materials, without or with high-pressure autoclave, under inert or active gas pressure, and the required control systems, are described. A broad description of the liquid encapsulation method is given, and construction details are contained in the figures. Special attention is given to the growth of gallium phosphide crystals and to the preparation of the starting material from the elements.(3)], and GaP [rap 1470~ (4)] decompose into their volatile components far below their melting points so that crystals can be grown from the melt only under pressure. Since large crystals can be grown from the melt faster and hence more inexpensively than by other methods, the need for initially costly pressure equipment is no longer a major deterrent.As usual in many fields, the long period of dormancy in which only a few devoted enthusiasts do the exploratory work, without much response, is over for crystal growth from the melt under pressure. Recently it became the focus of attention. This was caused by the coincidence of an industrial need for GaP crystals for electroluminescent diodes, triggered by the achievement of high efficiency in the visible, and the achievement of large GaP single crystals made by pulling through a boric oxide blanket under pressure.'Many of the results described here are scattered in government contract and conference reports so that a review of this increasingly important field is now timely. The results of other workers in this field are included. Most of the methods described below have actually been tested by us, so that their advantages and disadvantages can be related with authority.The paper is organized by describing the techniques in sequence of increasing complexity and refinement, which coincides frequently with the chronological order of their conception. Since materials synthesis is closely intermeshed with crystal growth, the synthesis methods are not described separately, but within the proper context. We treat Bridgman and Czochralski methods under high inert gas pressure and under cation or anion vapor pressure, the necessary equipment, control systems as they become necessary, and material synthesis from the elements. Since it is of prime importance now, we describe in detail crystal growth using liquid encapsulation, published by Metz, Miller and Mazelsky (5) in 1962, applied to GaP first by Bass and Oliver (6) at SERL, and amplified by our own results (7).The paper contains, besides numerous new scientific results, practical experiences and technological innovations, especially in the figures. The paper is confined to techniques and methods; properties of the prepared crystals have been and will be described elsewhere. Resistance Heater MethodsBridgman growth under high inert g...

Vertical Bridgman Growth of Binary Compound Semiconductors

“…Alternatively, the injection method developed by A.G. Fisher [131] has been applied for the synthesis of InP and GaP. Red phosphorus is controlled sublimated in a separate compartment and reacted with molten gallium and indium in a pBN crucible covered by boron oxide encapsulant.…”

Fundamentals of the CdTe synthesis

“…The previous descriptions of synthesis in both vertical and horizontal configurations show how hazardous the reaction can be in the liquid state. That is why the pressurisation under an inert gas in an autoclave to compensate the high pressures developed during the reaction of formation has been proposed either originally without encapsulant [4] or more recently with B 2 O 3 as an encapsulant [5]. This process makes use of sophisticated and expensive apparatus and makes it difficult to adjust precisely the stoichiometry by weighing large amounts of material.…”