極化效應對深紫外光氮化鋁鎵發光二極體的特性影響之模擬與分析

The Simulation and Analysis of Polarization Effect Upon Deep Ultraviolet AlGaN Light-emitting Diodes

盧宗宏(Tsung-Hung Lu) ； 黃滿芳(Man-Fang Huang)

《光學工程》 96期 (2006/12) Pp. 32-41

https://doi.org/10.30011/OE.200612.0005

摘要

在注重環保的現代，開發低污染、省電的照明設備是當前我們所要努力的目標。本文即是在看好氮化鋁鎵這個材料，可以發出250 nm到260 nm之間的深紫外光源，以用來激發現有日光燈用的高效率螢光粉進而放出白光。然而，由於氮化物材料本身的特殊結構以及至今仍未找到晶格匹配的基板來成長氮化鋁鎵，其所引起的極化效應將嚴重影響氮化鋁鎵發光二極體的特性，本文即在考慮極化效應的影響下，藉由Crosslight公司的模擬軟體－APSYS，對深紫外光氮化鋁鎵發光二極體的特性作理論分析。本文主要分為三個部份來探討深紫外光氮化鋁鎵發光二極體輸出功率，一是量子井的個數對輸出功率的影響；二是量子障對載子侷限的影響；三是井寬對輸出功率的影響。模擬結果顯示，當深紫外光氮化鋁鎵發光二極體具單一量子井，井與障的鋁含量差異盡可能的小，且井寬在1.5 nm時，發光二極體會有最佳的輸出功率。

關鍵字

氮化鋁鎵 ； 模擬分析 ； 深紫外光發光二極體 ； 白光 ； 極化效應 ； APSYS

並列摘要

AlGaN is an important semiconductor material for deep ultraviolet (UV) light emitting diodes (LEDs) with emitting wavelengths of 250 to 260 nm which is used for white LED application by pumping traditional fluorescent lamp phosphors. However, Ⅲ-Ⅴ nitrides in their hexagonal wurtzite structure and lattice-mismatched substrate possess large spontaneous polarization and piezoelectric coupling fields. These polarization fields significantly affect the band diagrams of quantum wells and hence the properties of AlGaN LEDs. In this report, the theoretical analysis for the deep UV AlGaN LED with the consideration of the polarization effect was done. The main purpose of this study is to optimize the quantum well (QW) structure for the AlGaN LED so that the output power of the LED can be maximized. Both the optical and electrical properties of the QW AlGaN LED have been simulated to investigate the effect of spontaneous and piezoelectric polarization upon the performance of the AlGaN LEDs. The theoretical analysis was done using the APSYS software from Crosslight Inc. We have found that under the influence of the polarization, both the electron and hole distributions inside QWs become non-uniform. The recombination efficiency and thus the output power of the AlGaN LED are greatly reduced. Moreover, our simulation results suggest that the higher output power is obtained when the number of the quantum wells is one with a width of 1.5 nm and the barrier layer with small Al composition for deep UV AlGaN LED.

並列關鍵字

AlGaN ； Numerical simulation ； wurtzite ； UV LED ； APSYS ； polarization effect ； white LED