Study of Time-Resolved Optically Detected Magnetic Resonance in Semiconductors

我们建立了工作在9.6 GHz和2K的时间分辨光学检测磁共振(TRODMR)测量装置，用5 ns的脉冲N_2和10 ns的准分子激光泵浦的染料激光作为脉冲激发源。利用该装置，我们对a-Si：H，a-&lt；Si_(1-x)N_x&gt；：H和a-Si：H/a-&lt；Si_(1-x)N_x&gt；：H超晶格进行了TRODMR实验。得到了以下结果和结论：1.首次观测到了a-Si：H中尾电子引起的ODMR信号。因此，在脉冲激发后，尾电子与在A中心和/或价带尾部的陷阱空穴的辐射复合被阐明为微波脉冲和用于测量的门脉冲的延迟时间的函数。对于a-Si：H/a-&lt；Si_(1-x)N_x&gt；：H超晶格，从A中心共振处发光强度随&lt；t_d&gt；的相对变化的结果推断了势垒层(a-Si：H)中电子和空穴的限制效应。对于界面不含大量缺陷的超晶格，与a-Si：H大块薄膜相比，通过薄势垒层中的悬挂键进行的非辐射复合被抑制。通过观察a-Si：H，a-lt；a-&lt；Si_(1-x)C_x&gt；：H和a-lt；Si_(1-x)N_x&gt；：H和a-lt；Si_(1-x)N_x&gt；：H中的g&lt；相似或等于&gt；4ODMR信号和宽的g&lt；相似或等于&gt；2ODMR信号，研究了三重态激子复合。通过这些研究，我们得出结论，TRODMR技术为阐明半导体中复合过程和复合中心的性质提供了强有力的手段。

We have set up the apparatus for time-resolved optically detected magnetic resonance (TRODMR) measurements operating at 9.6 GHz and 2 K. A dye laser pumped by either a pulsed <N_2> laser of 5 ns or a pulsed excimer laser of 10 ns was used as a pulsed excitation source. Using such equipment, we have carried out TRODMR experiments on a-Si:H, a- <Si_(1-x)N_x> :H and a-Si:H/a- <Si_(1-x)N_x> :H superlattices. The following results and conclusions have been obtained:1. The ODMR signal due to tail electrons in a-Si:H was observed for the first time. Thus, radiative recombination of tail electrons with trapped holes at the A centres and/or the valence band tail was clarified as a function of delay time of the microwave pulse and the gate pulse for the measurement, <t_d> , after a pulsed excitation.2. For a-Si:H/a- <Si_(1-x)N_x> :H superlattices, the confinement effect of electrons and holes in the well layer (a-Si:H) was inferred from the results of relative change in the luminescence intensity at the A centre resonance as a function of <t_d> . For superlattices not containing a number of defects at the interfaces, nonradiative recombination through dangling bonds in thin well layers was found to be suppressed compared to that for a-Si:H bulk films.3. Triplet exciton recombination was investigated by observing the g <Similar or Equal> 4 ODMR signal and the broad g <Similar or Equal> 2 ODMR signal in a-Si:H, a- <Si_(1-x)C_x> :H and a- <Si_(1-x)N_x> :H. From TRODMR experiments, it was concluded that triptet excitons decay with a time constant of <about> 1 ms in a-Si:H. From these investigations, we conclude that TRODMR technique provides a powerful means for elucidating recombination processes and nature of recombination centres in semiconductors.