C. L. Reynolds

Effect of p-doping profile on performance of strained multi-quantum-well InGaAsP-InP lasers

Leakage of electrons from the active region of InGaAsP-InP laser heterostructures with different profiles of acceptor doping was measured by a purely electrical technique together with the device threshold current. Comparison of the obtained results with modeling data and SIMS analysis shows that carrier leakage of electrons over the heterobarrier depends strongly on the profile of p-doping and level of injection. In the case of a structure with an undoped p-cladding/waveguide interface, the value of electron leakage current can reach 20% of the total pumping current at an injection current density of 10 kA/cm at 50/spl deg/C. It is shown that carrier leakage in InGaAsP-InP multi-quantum-well lasers can be minimized and the device performance improved by utilizing a p-doped separate-confinement-heterostructure layer.

Wavelength chirp and dependence of carrier temperature on current in MQW InGaAsP-InP lasers

In this paper, we derive a relation between the wavelength chirp and carrier temperature in semiconductor lasers. The coefficient relating the change in carrier temperature and chirp is expressed in terms of the temperature derivative of the optical gain, and two parameters describing the variation of refractive index produced by the variation of optical gain due to change of carrier quasi-Fermi level separation or carrier temperature. We have measured these parameters for MQW InGaAsP lasers, Using this data, we estimated the rate of the temperature increase with current above threshold in these devices, which is 0.13 K/mA.

Experimental study of physical parameters of semiconductor lasers

We discuss various experimental methods for measurements of the optical gain, transparency wavelength and optical loss. We discuss existing methods as well as newly developed. It is also shown how this set of measurements allows for characterization of other laser parameters, such as linewidth enhancement factor, differential gain, and wavelength chirp. We illustrate how these techniques are used for improving the laser performance for different applications.

Simulation of carrier dynamics in multiple-quantum-well lasers

We study the impact of carrier dynamics on the characteristics of InGaAsP/InP multi-quantum well lasers through detailed simulations and experiments. The device characteristics were simulated including carrier transport, capture of carriers into the quantum wells, quantum mechanical calculation of the levels and optical gain in the wells and solution for the optical mode. The simulations were self consistent for each value of device bias. The device characteristics studied include static light-current-voltage curves, dynamic small signal impedance and the small signal modulation of the light output. The comparison between simulation and experiment constrains the capture rate for these devices. The simulations suggest that the modulation response of these devices is not fundamentally limited by the carrier transport for the frequency range studied. The trends are understood in terms of sequential transport through the multi-quantum well active region.

Optimization of p-doping profile of 1.3-/spl mu/m InGaAsP/InP MQW lasers for high-temperature operation

It was shown theoretically and experimentally that an increase of p-doping concentration in the vicinity of a separate confinement heterostructure (SCH) of 1.3-/spl mu/m multiple quantum well (MQW) InGaAsP-InP lasers leads to improvement of the device temperature performance. Tne present work shows that alignment of p-doping profile within the SCH layer allows us to achieve even lower threshold current and to minimize temperature sensitivity of external efficiency.

Differential gain in 1.3-/spl mu/m InGaAsP/InP MQW lasers with p-doped active region

Summary form only given. We measured the temperature dependence of differential gain of 1.3-/spl mu/m InGaAsP-InP MQW FP and DFB lasers with the same design and two different doping profiles: moderately (2/spl middot/10/sup 17/ cm/sup -3/) and heavily (2/spl middot/10/sup 18/ cm/sup -3/) Zn doped active region. SIMS was applied to control doping levels. Differential gain values was obtained from corresponding RIN measurements. Experiments showed that the change of the active region doping level from 2/spl middot/10/sup 17/ cm/sup -3/ to 2/spl middot/10/sup 18/ cm/sup -3/ leads to a 50% increase of the differential gain for FP lasers at 25/spl deg/C.

Microscopic simulation of optical gain in multi-quantum well lasers

Detailed microscopic simulations are required to explain the observed optical gain in MQW laser diodes. The accuracy of the simulation is encouraging evidence that the physical models are correct and supports future optimization through simulation.

Role of doping profile on semiconductor laser performance: simulation and experiment

Summary form only given. It is widely known that the doping near the active region of a semiconductor laser has important consequences for the device performance, e.g. leakage current and modulation response. However, a clear microscopic picture is still needed. In this paper, we show that p-i junction placement controls laser output characteristics, in agreement with predictions of microscopic simulation. However, the same doping profile can not simultaneously optimize the static output characteristics and the high speed modulation response.

Temperature dependencies of output characteristics of 1.3-μm InGaAsP/InP lasers with different profiles of p-doping

Temperature dependencies of the threshold current, device slope efficiency and heterobarrier electron leakage current from the active region of InGaAsP/InP multi-quantum-well lasers with different profiles of acceptor doping were measured. We demonstrate that the temperature sensitivity of the device characteristics depends on the profile of p- doping, and that the variance in the temperature behavior of the threshold current and slope efficiency for lasers with different doping profiles cannot be explained by the change of the measured value of the leakage current with doping only. We show that doping of the p-cladding/SCH layer interface in InGaAsP/InP multi-quantum-well lasers leads to improvement of the device temperature performance. We also show that doping of the active region increases the value of the optical loss without degradation of characteristic temperature T0.