第四章中我们讨论掺氮磷化镓的光学特性,我们对一片掺氮磷化镓晶片做变温与变功率的光激萤光法测量,藉由掺氮磷化镓来研究均电性掺杂的特性,从参考文献与我们所观察到的频谱结果可以知道均电性掺杂有吸引激子的特性,尤其在低温时更是明显,而且这种特性对样品的发光效率有很大的影响与帮助.第五章总结的部份是我们将前四章的内容做回顾与简单的结论.
ABSTRACT
In this thesis we focus on two major topics. The first topic is on the performance of As-based 850 nm vertical-cavity surface-emitting laser, in which we study the effect of different active-layer materials on the laser efficiency. In the mean time, we do detailed investigation on the characteristics of the distributed Bragg reflector. The second topic of this thesis concerns the optical property of the N-doped GaP. The main goal is to investigate the emitting spectra of the N-doped GaP under different temperatures and pump power levels. There are five chapters in this thesis. The first chapter is the introduction of the AlGaAs and InGaAsP materials, including lattice constant, energy band gap, optical and electrical properties. Furthermore, we compare the emitting efficiency of the AlGaAs based red LED with that of the LED based on other materials. Moreover, we discuss the effect of strain on material parameters and performance of laser devices. In addition, we also discuss the critical thickness of the bulk, quantum well, and super lattice structures under strain.
In the second chapter, we introduce the theory and properties of distributed Bragg reflector (DBR) and vertical-cavity surface-emitting laser (VCSEL). We use both the linear summation and matrix method to analyze the DBR. Then, we utilize the matrix optics and Mathcad software to simulate the influences of pair numbers and incident angle on reflectivity spectra of step and graded DBR. Furthermore, we discuss the characteristics of the top-emitting and bottum-emitting VCSELs.
We compare the light emitting efficiency of the GaAs/AlGaAs, InGaAs/AlGaAs and InGaAsP/InP single quantum well at 850 nm in the third chapter, and broach the quantum wells that result in the best and worst emitting efficiency into the active layer of VCSELs to do more complete analysis and comparison, including carrier concentration distribution, stimulated recombination rate, the curve of output power and main-side mode suppression ratio versus injection current, and the characteristic temperatures of devices with different active layers. Besides, we also measure the photoluminescence spectra under different temperatures and pump power levels and the transmission spectra at room temperature of a VCSEL sample. We then calculate the reflectivity spectra from the transmission spectra and have results compared with that obtained from numerical simulations to justify the correctness of the experiments and simulations.

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