应变Si1-xGex层中p型杂质电离常温和低温特性

本文采用解析的方法计算了应变Si1-xGex层中p型杂质电离度与Ge组分x、温度T以及掺杂浓度N的关系.发现常温时,在同一Ge组分下,随着掺杂浓度的升高,杂质的电离度的先变小,而后又迅速上升到1.在同一掺杂浓度下,轻掺杂时,杂质的电离度随Ge组分的增加先变大,而后几乎不变;重掺杂时,杂质电离能变为0后,杂质电离度为1.低温下,轻掺杂时,载流子低温冻析效应较为明显,杂质的电离度普遍较小,当掺杂浓度大于Mott转换点时,载流子冻析效应不再明显,电离率迅速上升到1.在同一Ge组分下,随着掺杂浓度的升高,杂质的电离度先变小,后变大,而后又迅速上升到1.在同一掺杂浓度下,轻掺杂时,杂质的电离度随Ge组分的增加变大;重掺杂时,杂质电离能变为0后,杂质电离度为1.

THE MINORITY CARRIER CONCERTRATION OF STRAINE Si1-xGex LAYERS AS A FUNCTION OF Ge DFRACTION TEMPERATURE AND IMPURITY CONCENTRATION

The ratio of hole concentration to impurity concentration is calculated analytically with the varing of the temperature T, Ge fraction x and doping concentration.It is found that with the given Ge fraction, the ratio of hole concentration to impurity concentration decreases at first, and then increased sharply to 1 with the increasing of doping concentration. With the given doping concentration, the ratio of hole concentration to impurity concentration increases more and more slowly with the increasing of doping Ge fraction x at 300 K. At low temperature,freeze-out is in evidence. The ratio of hole concentration to impurity concentration is very small.When the doping concentration is large than Mott doping concentration, the atio of hole concentration to impurity concentration increases to 1. With the given Ge fraction, the the ratio of hole concentration to impurity concentration first decreases and then increase quickly to 1with the increasing of the doping concentration. with the given doping concentration, the ratio of hole concentration to impurity concentration increases more and more slowly with the light doping. For heavily doped SiGe layers, the ratio of hole concentration to impurity concentration is 1 when the the iionization energy of impertities is 0 eV.