Reasarch And Improvement Of Minority Carrie Rlife Time Testor

Among the physics parameters which can reflect the propertiesof semiconductor materials and devices, minority carrier lifetimeplays a key role. The purity and lattice integrity of semiconductormaterials can be mirrored by minority carrier lifetime, which hasa great influence on the efficiency of solar cells. Adjustment anddivision of semiconductor materials in industry cannot go withoutthe detection of minority carrier lifetime.The first chapter provides some discuss of solar businessdevelopment, then emphasizes the importance of silicon wafertesting and leads to the testing of minority carrier lifetime atlast. The second chapter introduces the definition of minoritycarrier lifetime, and does a deep analysis about the recombinationprocess which has a great impact on the minority carrier lifetime.Then some popular methods of testing minority carrier lifetime will be introduced, with their principle and shortcomings andadvantages discussed and compared.Chapter three explains the principle of microwavephoto-conductance decay method, and shows the process of buildingthe tester setup. Minority carrier lifetime tester has a poorrepeatability caused by low signal-noise ratio. In order to solvethe problem，this paper analyzed the transmission features ofmicrowave in the rectangle waveguide. Then magic tee was analyzedroundly due to its essential function in the transmission andcoupling of microwave. It comes out that a large amount ofmicrowave energy was wasted during the transmission in the magictee, which directly and largely slashes signal-noiseratio.Circulator can cover magic tee s shortcomings. It cantransfer and couple microwave, at the same time, it has a tinyenergy loss, which leads to a better signal-noise ratio. Therepeatability rises from7%to3%after the improvement by changingmagic tee with circulator. At last,some supplement and discussion about the method willbe showed，especially the limitation and some point worth deeperresearch. Then some viewpoints about minority carrier lifetimetester will be provided.