藍光發光二極體不同量子井厚度的內部量子效率之研究

Abstract

本論文實驗之藍光LED，利用光致發光(Photoluminescence, PL)、電致發光(Electroluminescence, EL)、以及Advanced Physical Models of Semiconductor Devices (APSYS)模擬軟體等進行樣品的光學與電氣特性作分析。我們藉由改變輸入功率在於光致發光和電致發光的量測來探討低溫和室溫下影響InGaN/GaN之多重量子井發光二極體內部的量子效率(Internal quantum efficiency, IQE)之物理特性。 在電致發光量測時，發現當在低溫高電流注入下，因低溫而造成電洞載子濃度以及遷移率下降，電洞在量子井中的分布不均勻，且因為電洞的遷移率下降，造成更多的電洞無法有效的注入到量子井中而累積在靠近p-GaN的量子井中，另外也由於量子井中電洞的不足，造成更多的電子產生溢流現象，導致內部量子效率在高電流下會產生效率遽降的情況。 本論文實驗量測的 Sample 為三種不同量子井厚度的藍光 LED 分別為 1.5nm、2.0nm、2.5nm，分析其不同的發光特性，建立LED的等效模型，其可分為漏電流、輻射復合電流、非輻射復合電流、及高注入時產生的 overflow 電流。其中高注入的 overflow 電流亦引發了 Auger 效應，讓發光的效率隨電流增加而遽降。同樣的 Sample 量測光致發光(PL)的特性及APSYS模擬結果，也映證了 EL 的結果。

This experiment was use of photoluminescence (Photoluminescence, PL), electroluminescence (Electroluminescence, EL) and Advanced Physical Models of Semiconductor Devices (APSYS) simulation software such as samples for optical and electrical characteristics analysis. We change the input power for Photoluminescence and electroluminescence measurements to explore the impact on low temperature and room temperature for InGaN/GaN multiple quantum well LED internal quantum efficiency of the physical characteristics.

In the electroluminescence measurement, it was found that under high-current injected at low temperature. The hole concentration and mobility was trend down. The hole distribution was not uniform in the quantum well and because the hole mobility decreased, lead to more effective hole can not be injected into the quantum wells and the accumulated in close proximity to the p-GaN quantum wells. The quantum wells is also due to the lack of hole resulting in more electron overflow to p-GaN. Result the internal quantum efficiency droop on high current injection.

The experimental measurement of the Sample for the three different quantum well thickness for the blue LED, respectively, 1.5nm, 2.0nm, 2.5nm, to analyze the different light-emitting properties, the establishment of the equivalent LED model, which can be divided into the leakage current, Radiation composite current, non-radioactive compound current, and high injection current caused by the overflow. The high-injection current was lead to Auger effects that the efficiency droop with the current increase. The Photoluminescence (PL) and APSYS simulation result also same as Electroluminescence.