電流注入式微碟雷射之研製與特性分析

Abstract

由於微碟雷射內部迴廊模態體積小，又因有高的品質係數，因此能夠實現低臨界電流密度的優良特性。在本篇論文中，我們分別製作出直徑大小約10μm的電注入式量子井與量子點微碟雷射，並從78K至室溫範圍做變溫量測，探討模態位移量對溫度的相依關係。 我們InGaAsP量子井樣品製作微米尺度的微碟雷射，可作為光纖通訊的雷射光源應用。利用電子束微影、乾式蝕刻及濕式蝕刻技術，並結合平坦化製程技術，製作出的微碟雷射元件。利用直流電注入量測螢光頻譜，可發現在78K下，雷射臨界電流約28μA。而目前直流操作溫度可達250K，其臨界電流約為0.69mA。 我們的InGaAs/GaAs量子點樣品，則利用兩次濕式蝕刻來製作雙碟結構。而目前使用脈衝電流操作下，可發現在150K下，有最低的雷射臨界電流約150μA。室溫下仍可操作，臨界電流值約為0.65mA，且Q值高達3700。使用BCB包覆微碟共振腔，可降低整體有效折射率對溫度的變動量，使模態對溫度的敏感度降低，使紅移量變小。 在本篇論文中，我們成功地展示了電注入式的量子點與量子井微碟雷射具有極低的臨界電流與更佳的模態溫度穩定性，因此，有很高的潛力能夠應用在下一世代的積體光電模組與系統中。

Microdisk lasers play important roles of light sources with low power consumption in large-scale photonic integrated circuits. Microdisks whose cavities confine light to small volumes support high-Q whispering-gallery mode (WGM) resonances, so they are considered to be potential candidates for the next-generation semiconductor lasers used in optical long-distance telecommunications. In this thesis, we fabricated two kinds of current-injected microdisk lasers- InGaAsP quantum-well and InGaAs quantum-dot microdisk lasers with disk size about 10μm in diameter. We measured the mode shift with varied temperature from 78K to room temperature. We use InGaAsP quantum well samples to fabricate the electrically pumped microdisk laser devices, which can be further applied as laser sources in photonic integrated circuits. We have successfully fabricated disk lasers by e-beam lithography, ICP dry etching and selective wet etching techniques. Using a benzocyclobutene (BCB) polymer cladding which decreased redshift with varied temperature, the metal electrodes can be more easily made. We apply a DC current source for current injection. The threshold current is 28μA at 78K. The highest temperature where lasing can still be achieved is 250K. At this temperature, the threshold current for a 10-μm -diameter device was about 0.69 mA, and the Q factor is about 930. We fabricated InGaAs QD microdisk lasers using two-steps wet etching to produce the double-disk structure. From the electroluminescence spectrum of our InGaAs QD microdisks by pulse current injection, we can get the lowest lasing threshold current at 150K. Below 150K, the characteristics temperature is negative. We can operate the device which lasing threshold current is 0.65mA at room temperature, and the largest WGM quality factor observed is 3700.