Preparation of p — n Junctions by Surface Melting

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Abstract
A new method is described for preparation of p — n junctions in single‐crystal semiconductors: the upper part of a slice cut from a single‐crystal semiconductor is melted by radiation. Impurities of the opposite type than those present in the crystal are introduced into the melt. Upon slow solidification of the melt a single crystal is obtained with a p — n junction at the original position of the solid‐liquid interface. The method is capable of producing multiple junctions. The influence of (a) heater temperature, (b) forced cooling, and (c) thickness of the slice on the position of the solid liquid interface is calculated for a one‐dimensional model, assuming that the temperature difference between bottom and top of the semiconductor is small compared to the melting temperature of the semiconductor. The time constant characterizing the rate of reaching equilibrium conditions after a sudden small change in heater temperature is estimated.