Research About The Effect Of Minority Carrier Recombination Behavior On Injection Level

Surface photovoltage (SPV) measurement is an effective on-line monitoring tool for its non-contaminated samples, without destroying the sample morphology, as well as not affected from the basement or the body of samples. SPV also becomes a recognized standard measurement of testing minority carrier lifetime method in ASTM. In this thesis, a comprehensive overview based on the theory of the minority carrier generation and recombination have been presented. The minority carrier behavior is investigated by means of numerical calculation, experimental verification and results fitting on high injection level. So the laser light source replaced traditional light source of SPV technology for widely used and accurately measurement could be realized.In order to deeply understand about the minority carrier behavior in semiconductor under extreme condition, P-type silicon is calculated as an example to clarify the the influences of the recombination mechanisms, the carrier lifetime and the iron contaminated concentration on the injection level is discussed.SRH, Auger and Radiation recombination mechanisms were considered in body lifetime calculating. SRH recombination is the greatest contributor for body lifetime, while Auger and Radiation recombination can be approximately ignored whenηis low. But the contribution of Auger and Radiation recombination are increasing when r| is high. Moreover, SRH lifetime is increasing asηincreases when E_T locates in middle of band gap, and it reduces asηincreases when E_T locates in middle of band edge. Surface passivation treatment is applied on the samples to separate the lifetimes of the body and the surface. In this way the corresponding experimental changings of the carrier lifetime and the surface recombination velocity basing on different injection level are clarified respectively. The surface recombination velocity changes just oppositely against the body lifetime onη.In addition, Fe-B pairs are separated by different intensity laser light, then the lifetimes before and after the Fe-B pairs decomposition could be obtained. In this way, relationship of Fe concentration with injection level could be found. The results show that Fei is in this case -low injection level - about a 10 times stronger recombination center than FeB. And vice versa. It is also found that the value of Fe concentration coefficient C becomes increasingly a linear growth trend asηincreases gradually.The above results of theoretical calculation would meet the experimental data accordingly in the test range. So the best theoretical calculation parameters for in-depth understanding could be got. It provides basic datas and theory support for good understanding about the minority carrier behavior on high injection level, and also for widely application of SPV measurement with laser source.