Study Of Characteristics And Simulation Of VCSEL Based On ISE TCAD

The vertical-cavity surface-emitting laser (VCSEL) has the properties of lowthreshold current and high conversion efficiency. They are single-longitudinal modelasers and has small divergence angle for easier fiber coupling. VCSEL can be testedalready on the wafer and possible to fabricate two-dimensional arrays of VCSEL, so itis considered as one of the most important devices for MCM optical communications.The basic principles and structures are expounded in this thesis, and theconditions of laser generation are introduced from the view of semiconductor physics.Based on these, the vibration principle of the semiconductor laser has been explained.The key method and main technology which result in the evolution of the structure hasbeen summarized. Beside of this, the characteristics of light mode and the mainstreamnumerical solver for optical field has been described.Based on phenomenological method, the expression of threshold current forVCSEL with general rectangular section is derived in details from two basic rateequations. The formula shows that VCSEL threshold current is mainly determined bycavity loss, material gain curve, the actual light emitting area and the degree of leakagecurrent. According to the expression, the threshold current can be reduced from severalaspects, including lower cavity loss, reducing the light-emitting aperture and using thestrain quantum well material, etc. A possible modified threshold current expression forOxide-Confined Inner-connected VCSEL structure has put forward.The carriers capture model for quantum well simulation and the correspondingcontinuity equations for different regions of the device are expounded. VCSEL withrectangular cross-section are simulated by ISE TCAD. The simulator gives the basiccharacteristics, the relationship of material gain with injection current and the nearfield intensity distribution. The results show the threshold current is in the order of afew tenths of milliampere. With the increase of the emitting aperture, threshold currentincreases and the optical intensity distribution of the1st order transverse modebecomes more scattered. For the active region with the unity of current density, thethreshold current shows a quadratic relationship with light-emitting aperture.