Temperature Dependent Recombination Lifetime in Silicon: Influence of Trap Level
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TEMPERATURE DEPENDENT RECOMBINATION LIFETIME IN SILICON: INFLUENCE OF TRAP LEVEL ANDRZEJ BUCZKOWSKI, ZBIGNIEW J. RADZIMSKI, YOSHI KIRINO, FUMIO SHIMURA AND GEORGE A. ROZGONYI North CarolinaState University,Dept. of MaterialsScience and Engineering, Raleigh, NC 2 76957916 ABSTRACT:
This paper discusses the temperature dependence of recombination lifetime in a variety of silicon materials using energy level as a parameter. A theoretical approach based on the Shockley-Read-Hall theory for energy level calculations has been used. Various types of defects created by introducing impurities, dislocations and grain boundaries into silicon wafers were studied. Results are presented for Czochralski grown Si wafers intentionally contaminated with gold and chromium, EFG ribbon with varying concentration of oxygen, web ribbons with extended defects and contaminants, large grain polycrystalline material, and Si/Si-Ge/Si heterostructures with varying misfit and threading dislocation density. INTRODUCTION Minority carrier recombination lifetime is a convenient parameter for semiconductor material evaluation, since it is significantly affected by defect-induced traps located within the forbidden gap. The recombination depends not only on the energy level location, but also on the trap concentration and capture cross section. Therefore, in order to describe accurately the recombination behavior of defects, these three components have to be characterized. A commonly used technique for this purpose is deep level transient spectroscopy (DLTS) [1]. Although this technique is very powerful, it is relatively complicated, time consuming and requires some sample preparation. However, in many cases determining the recombination lifetime and the activation energy of a specific defect or impurity is sufficient enough to evaluate material quality. For this purpose only the temperature dependence of recombination lifetime 'r(T) is required. This dependence can be obtained with contactless, high throughput and nondestructive techniques for which no device fabrication is required. This paper discusses the 'r (T) dependence in a variety of silicon materials using defect energy level as a parameter. A theoretical approach based on the Shockley-Read-Hall theory for energy level calculations has been used. Various types of defects created by introducing metal impurities, grain boundaries or misfit dislocations into Si wafers were studied. A laser / microwave DLTS technique (LM-DLTS) [2] operating in the temperature range from 273 K to 523 K was used as a non destructive, contactless tool for lifetime and activation energy determination of bare non-processed silicon. ANALYSIS Multiphonon recombination under low excitation conditions as described by the ShockleyRead-Hall theory (SRH), is assumed to be the dominant mechanism responsible for the minority carrier lifetime. Auger and radiative recombinations are neglected, since only lightly doped silicon material is considered here. Special attention is paid to the temperature influence on recombination p
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