850nm Vertical Cavity Surface Emitting Lasers

Vertical-Cavity Surface-Emitting Lasers (VCSELs) devices were known gradually for its advantage, such as good beam quality, low threshold currents, easy to two-dimensional array integration and low manufacturing cost. Currently, VCSELs have been widely used in optical communication devices, optical interconnects, computer systems, display, storage, medical, industrial processes and military fields. Especially, the high-power applications of VCSELs devices have the extensive prospects. Nowadays, larger array of integration is used generally to improve the output power of devices, but the drive current is increased at the same time integration is increased because that light-emitting unit of array is parallel. If each light-emitting unit mesh is 300μm, pitch is 500μm, a three-inch chip can be integrated over seventy thousand light-emitting unit. If the drive current of each light-emitting unit is 3A, then a three-inch chip will require more than 210,000A of the current source, but such a large current source can be not obtained. Currently the largest international source of pulsed current does not exceed 5kA. Drive current source problem is the problem facing the world, application of high-power VCSELs will be seriously hampered if this problem is not solved. For the traditional closed VCSEL, we should fill the groove with the polyurethane to make sure wire bonding area and annular electrode join together and then etch to make the surface planar. But filling the polyurethane will prevent heat dispersing and etching will bring optical loss which will also make the process more complex. A VCSELs in series structure is reported to solved the current source problem, and then a non-closed structure is reported to solved the heat dispersing problem. In this thesis, detailed analysis and research on design method, theoretical calculations and process technology of VCSELs devices are also described. Main content and innovations is as follows:1. The VCSELs array devices to be connected together in series, without improving drive current but increasing the output power. In the same injection current, the output power of four-chip devices in series and two-chip device in series was about 4 times and 2 times as that of the single device, therefore, the in series structure could greatly increased output power without improving drive current; This structure of the device is used in the projects in this group and obtains a good evaluation; At the same time the structure authorized by the State obtained a patent for invention.2. The non-closed loop groove is etched when the mesa is etched. The wire bonding area and annular electrode join together in this structure, so filling the polyurethane is unnecessary. It will not only improve heat dispersing, avoid optical loss brought by etching but also simplify the process due to the non-closed structure.3. The theoretical calculation of the threshold current, differential quantum efficiency, side-mode case, the heat features and pump efficiency of active region was described in this paper; The features and advantages of the graded DBRs were also analyzed theoretically; The effect of carrier concentration, injection current distribution and carrier transport mechanisms on the spatial hole burning(SHB), and the effect of SHB on the performance of VCSELs devices were analyzed; The current flowing through the DBRs was calculated and the current transport mechanism was described; The internal heating effect on the performance of the VCSELs devices was analyzed and a simple thermal analysis model was described.4. A reasonable top emission process was designed, and each steps of this process were optimized; The effect of each process step on the device performance was analyzed detailedly.