摘要
本論文中，我們藉由光激發光及電激發光的激發方式，探討因為鍺之再激收效應造成直接能隙發光效率減少的現象。 表面複合速度可影響等效載子壽命，進而改變光激發之載子分佈。因為鍺之在吸收效應為距離的函數，減少鍺的背面表面複合速度使載子更深入晶片深處，增強直接能隙的放光之再吸比例。增加鍺的背面表面複合速度使載子更集中於晶片表面，減少直接能隙的放光之再吸比例。直接能隙或非直接能隙之放光比例都可藉由物理模型去加以模擬並解釋。 在電激發光中電子會因電場而漂移，在垂直結構下因垂直的電場使電子飄移至晶片之深處而增加再吸收效應。控制電場方向製作水平結構之鍺發光二極體電可讓更多電子聚集在裝置表面，增加高能階的電子濃度及降低再吸收影響，使直接能隙之放光效率增加。水平結構之電極遠近亦會影響電流聚集程度而改變直接能隙之放光效率。
並列摘要
In this thesis, we discussed the reduction of direct bandgap emission which is caused by the reabsorption effect of Germanium emission. The variation of effective lifetime caused by different surface recombination velocity affects the carrier distribution profile. As the reabsorption effect is a function of distance, carriers diffuse to the deeper side of wafer which enhances reabsorption effect by decreasing back surface recombination velocity. By the way, extremely large back surface recombination velocity leads the carrier to crowd at the surface to reduce reabsorption effect. The emission ratio of direct and indirect transition can be explained by the carrier distribution profile which is simulated using Sentaurus. In the vertical germanium light emitting diode structure, electrons will be drifted to the deeper side of wafer by electric field which enhances reabsorption effect. The lateral germanium light emitting diode structure allows electrons to crowd at the surface which not only moves the electron Fermi level upwards and the increase in electron population in direct valley enhance the luminescence but also reduces reabsorption effect. The crowding effect increases with the closer lateral contact.
參考文獻
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