The Absorption In Tunneling Junction And Its Influence On The Characteristics Of Novel High Power Semiconductor Lasers

Semiconductor lasers have many advantages such as small volume, high power conversion efficiency, low dissipation of energy, direct current modulation, high rate of data transmission, high reliability, long lifetime and wide lasing spectrum etc. Because of these advantages semiconductor lasers have been heavily used in many fields. Particularly, the high power semiconductor lasers are the hotspot and focus of current research and industrialization. In this dissertation, we firstly analyzed the main problems and limits of high power semiconductor lasers with ordinary structure, then introduced the theory of the novel high efficiency high power tunneling regenerated QW lasers proposed be professor Shen Guangdi. By comparing the new type lasers with the ordinary ones, we analyzed the characteristics such as: inner quantum efficiency, external differential quantum efficiency, power conversion efficiency and threshold current density, and summarize the main advantages of the novel high efficiency high power tunneling regenerated QW lasers. This new type lasers will have novel high quantum efficiency larger than 1, can achieve high output power at relative low current density and overcome the main hinder of ordinary high power semiconductor lasers: catastrophic optical damage (COD) by increase the size of facula. Basing on the analysis above, we also summarized two main problems that should be considered carefully in the design of this new type laser. Using the new theory, we designed and fabricated InGaAs/GaAs/AlGaAs tunneling regenerated QW lasers (X980nm). By measuring and analyzing the characteristics of these new type lasers, we proved the physical theory of the novel high efficiency high power tunneling regenerated QW lasers and obtain the devices with the novel high quantum efficiency larger than 1. According to the results of the experiments, we found that it is difficult for the new type laser to realize the TEO mode. The reason of it, we presume, is that the GaAs tunneling junction has strong absorption loss of the 980nm light. In order to verify our presumption, we completely analyzed the absorption mechanisms in the tunneling junction and qualitatively find two main mechanisms that are likely to result in the strong absorption loss of the 980nm light: a) The absorption loss of inner energy band transition caused by the high free carrier density in the non-depletion layers b) The absorption loss of inter energy band transition caused by the strong electric field and the energy gap shrinkage from the band tails at the interface of Tunnelingjunction of the depletion layers.In order to know in detail the infiuence of the free carrier concendation on theabsorption coefficient of the heavily doped GaAs just under the absorption edge, wemeasured the absorption coefficiellt of Gsas with different doping concentrations in thespectrum from 900-l600nm by the method of dual-beam spectrOphotOmeter Accordingto the results of the experiment, we found the relationship between the absorptioncoefficient and the doping concentration at the wavelength of 980nm by the method oflinear fit. Also we estimated the absorption coefficient in the depletion layers using theexperiential equation. All the work done above allowed us to optimize and design thetunneling junction which has small absorption loss of 980nm light.According to the results of analysis, computation and experiment of the absorptionloss in the trieling junction, we optimized and designed a new strucfore of thetunneling junction with small absorption loss, then utilized it in the novel three activeregion tunneling regenerated QW lasers and finally obtai...