| Summary: | 博士 === 國立交通大學 === 光電工程研究所 === 105 === Recently, GaAs- and GaN-based materials had shown its superior potential for Opto-Electronic device applications, which is due to its emission wavelength can cover from near ultra violet to near infrared wavelength by tuning the alloy composition. And the high emission efficiency due to its direct band gap character. On the other hand, compared to edge-emitting lasers (EELs), vertical-cavity surface-emitting lasers (VCSELs) have low power consumption, circular beam shape, high bandwidth and low divergence angle. The well-established GaAs-based VCSELs are widely used for the fiber communications. However, in order to meet the requirement of the next generation high speed Ethernet standard. The bandwidth of GaAs-based VCSELs still have room for improvement. For the GaN-based VCSELs, since the first electrically pumped GaN VCSEL was demonstrated at 2007 by National Chiao Tung University. Researchers devoted hugh efforts on the further improvement of GaN VCSEL by increasing the epitaxy quality and optimizing the fabrication process. However, the unbalance of electron/hole mobility and Auger recombination lead to a low injection efficiency in GaN VCSEL. And there has no much efforts on this issue.
In this thesis, the theoretical simulation is conducted to optimize the performance of GaAs and GaN VCSELs. For the GaAs VCSEL, the intrinsic and extrinsic limitation are released via the use of highly strained MQW, multiple oxide layers and modulation doping in DBR. Furthermore, AlAs/GaAs bottom DBR is designed for high thermal conductivity character. For the GaN VCSEL, superlattice electron blocking layer (EBL) is designed to compare with the bulk EBL. Compared to the bulk EBL, superlattice EBL can release the QCSE effect, and furthermore, it provides a virtual energy potential to block the electrons from escaping the MQW.
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