Gleb E. Shtengel

Role of p-doping profile in InGaAsP multiquantum well lasers: comparison of simulation and experiment

We study the role of p-doping on the characteristics of InGaAsP/InP multi-quantum well lasers through detailed simulations and experiments. The static and dynamic characteristics of a series of 1.3 μm lasers with varying p-i junction placement were measured. 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 and carried out as a function of device bias. The simulations account for the trends observed with p-doping profile. In particular, the simulated optical gain and small signal resonance frequencies agree well with the measurements. The trend of larger resonance frequency with increased p-doping in the active layer of the laser depends on both the gain and the carrier transport through the multi-quantum well region.

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.

Measurement of chirp in semiconductor lasers using interferometric intensity noise

Frequency chirp in semiconductor lasers is a critical physical parameter for both analog and digital communications system performance. Here we describe a method for measuring chirp which uses the interferometric properties of standard fiber instead of a separate interferometer.