Effect of auger recombination on the threshold characteristics of gain-guided InGaAsP lasers

Experimental and theoretical results are presented to study the effect of Auger recombination on the threshold current of gain-guided InGaAsP lasers. A comparison of theory and experiment suggests that Auger recombination should be included for a reasonable agreement between them. It is shown that a rapid increase of the threshold current for narrow stripes is due to the combined effect of index anti-guiding and Auger recombination. Our deduced values of the Auger coefficient at 1.3 and 1.55 ?m indicate that it increases rapidly with decreasing bandgap.     

Threshold characteristics of λ=1.55 µm InGaAsP/InP heterolasers

Temperature dependences of the threshold characteristics of InGaAsP/InP quantum well (QW) lasers have been studied. The main contribution to the threshold current is made by the thresholdless Auger recombination. The observed power-law temperature dependence of the threshold current is explained by the predominance of the thresholdless Auger recombination in QWs over the threshold Auger process.     

Auger recombination effect on threshold current of InGaAsP quantum well lasers

The Auger recombination effect on the threshold current of the InGaAsP quantum well (QW) laser is studied theoretically. All possible transitions between the quantized subbands of two-dimensional carriers are taken into account in evaluating the radiative process with thek-selection rule and the Auger process. The calculated threshold current agrees well with the reported experimental results for 1.07 μm InGaAsP QW lasers. The Auger component of the threshold current and its temperature dependence strongly depend on the QW structure, resulting in the necessity for an elaborate QW structure design, although both cannot be optimized at the same time. A design procedure is elucidated for a structure which gives the lowest threshold current density for the 1.07, 1.3, and 1.55 μm InGaAsP QW lasers.     

Interband Auger recombination in InGaAsP

The interband Auger recombination lifetimes of two Auger processes have been calculated to correlate measured threshold current densities and carrier lifetimes for InGaAsP and InGaAsSb lasers. Good aggreement with experimental data was obtained for lasers with low nominal threshold current densities. These results demonstrate the importance of Auger recombination in the threshold characteristics of InGaAsP/InP lasers.     

Theory of the temperature dependence of the threshold current of an InGaAsP laser

The threshold current of an InGaAsP laser is calculated, where the radiative emission, reflection and absorption losses, and Auger recombination are considered. Moreover, the enhancement of the threshold carrier density at high temperatures is an important point. A mechanism for this enhancement is discussed. Then we obtain an excellent agreement with the measured temperature dependence of the threshold current, in particular the To-values for T≷TBand the break point TB. The reason for this break point is that the radiative recombination dominates for T < TB, whereas the strongly temperature dependent valence band Auger process becomes more and more important for T > TB. It is this process which causes the strong increase of the threshold current in the room temperature range.     

A numerical calculation of auger recombination coefficients for InGaAsP/InP quantum well heterostructures

Auger recombination coefficients are calculated numerically for InGaAsP/InP quantum well heterostructures. In narrow quantum wells, the quasi-threshold and thresholdless mechanisms mainly contribute to the Auger recombination coefficient. For the processes involving two electrons and a heavy hole (CHCC) or an electron and two heavy holes with a transition of one of the holes to the spin-orbit split-off band (CHHS), the Auger recombination coefficients depend on temperature only slightly in a wide temperature range. The dependence of the Auger coefficient on the quantum well width is analyzed and found to be nonmonotonic.     

The performance of double active region InGaAsP lasers

The light-current characteristic and temperature behavior of the double-carrier-confinement (DCC) InGaAsP laser are shown to be largely determined by Auger recombination. The carrier distributions in the two active regions, especially their relative fractions, play a major role in device behavior. A self-consistent, comprehensive numerical laser model is used to analyze a set of devices showing that superlinearity and possibly bistability are due to saturable absorption in the second active region and that a high characteristic temperature is usually tied with a higher threshold current density because of substantial Auger recombination rates in this type of device     

A comparative study of temperature sensitivity of InGaAsP andAlGaAs MQW lasers using numerical simulations

We used numerical simulation to compare the temperature sensitivity of an InGaAsP MQW laser emitting at 1.55 μm and an AlGaAs MQW laser at 0.82 μm. By artificially changing the InGaAsP laser gradually into a structure similar to the AlGaAs laser, we gained quantitative insight into how each material or structural parameter causes the relatively low T₀ of the InGaAsP MQW laser. Using a typical MQW structure we demonstrated the relative importance of parameters involving Auger recombination, current leakage over the quantum barrier, optical confinement and band offset. We found that if these parameters were made the same as the AlGaAs laser, the T₀ of the InGaAsP laser was even better than that of the AlGaAs laser. Our numerical simulation confirmed that the Auger recombination is the main cause of low T₀ in MQW InGaAsP lasers. We also discovered that thermal current leakage over the barrier and Auger recombinations are correlated with each other and both factors must be improved to increase the T₀ of InGaAsP lasers to that of AlGaAs lasers     

Temperature dependence of the lasing characteristics of the 1.3 µm InGaAsP-InP and GaAs-Al0.36Ga0.64As DH lasers

We report here our experimental observations on the temperature dependence of threshold current, carrier lifetime at threshold, external differential quantum efficiency, and gain of both the 1.3 μm InGaAsP-InP and GaAs-AlGaAs double heterostructure (DH) lasers. We find that the gain decreases much faster with increasing temperature for a 1.3 μm InGaAsP DH laser than for a GaAs DH laser. Measurements of the spontaneous emission observed through the substrate shows that the emission is sublinear with injection current at high temperatures for the 1.3 μm InGaAsP DH laser. Such sublinearity is not observed for GaAs DH lasers in the entire temperature range 115-350 K. The experimental results are discussed with reference to the various mechanisms that have been proposed to explain the observed temperature dependence of threshold of InGaAsP DH lasers. We find that inclusion of a calculated nonradiative Auger recombination rate can explain the observed temperature dependence of threshold current, carder lifetime at threshold, gain, and also the sublinearity of the spontaneous emission with injection current of the 1.3 μm InGaAsP-InP DH laser. Measurement of the nonradiative component of the carrier lifetime (τA) as a function of injected carrier density (n) shows thattau_{A}^{-1} sim n^{2.1}which is characteristic of an Auger process.     

Determination of the wavelength dependence of Auger recombinationin long-wavelength quantum-well semiconductor lasers using hydrostaticpressure

The variation of the threshold current of an unstrained 1.48-μm InGaAsP quantum-well (QW) laser has been measured as a function of hydrostatic pressure up to 27 kbar. We combine this result with theoretical calculations to extract the bandgap dependence of the Auger coefficient, C, over a range of 200 meV. We find that over this range C reduces by a factor of about three. We have calculated the bandgap dependence of the main Auger processes and conclude that the dominant Auger process over this wavelength range could either be the phonon-assisted CHCC process or the band-to-band CHSH process. Based on this result, we have estimated the threshold current density of strained and unstrained lasers with wavelengths ranging from 1.75 to 1.3 μm using both these processes. We get good agreement between theory and experiment in both cases and show that Auger recombination is the dominant current contribution in 1.5- and 1.3-μm devices     

Radiative and nonradiative recombination law in lightly doped InGaAsP lasers

We analyse data relating to radiative and nonradiative recombination in a 1.3 ?m InGaAsP laser operating below threshold. The results show that with a lightly doped active region the radiative recombination coefficient decreases with increasing carrier concentration in accordance with previous theoretical results. Further, they indicate that the Auger nonradiative recombination is relatively small.     

Dominance of auger recombination in InGaAsP light emitting diode current-power characteristics

Output power saturation in 1.3-µm InGaAsP light emitting diodes with various active layer thickness has been investigated experimentally in a wide temperature range. Nonradiative recombination current with strong injected carrier density dependence, which is responsible for saturation, was found to be proportional to active layer thickness and almost independent of temperature under constant injected carrier density conditions. External quantum efficiency at a constant injected carrier density was found to be independent of active layer thickness. These results indicate strongly that Auger recombination is the dominant nonradiative process in InGaAsP light sources.     

Localized Auger Recombination in Quantum-Dot Lasers

We have calculated radiative and Auger recombination rates due to localized recombination in individual dots, for an ensemble of 10⁶ dots with carriers occupying the inhomogeneous distribution of energy states according to global Fermi-Dirac statistics. The recombination rates cannot be represented by simple power laws, though the Auger rate has a stronger dependence on the ensemble electron population than radiative recombination. Using single-dot recombination probabilities which are independent of temperature, the ensemble recombination rates and modal gain decrease with increasing temperature at fixed population. The net effect is that the threshold current density increases with increasing temperature due to the increase in threshold carrier density. The most significant consequence of these effects is that the temperature dependence of the Auger recombination rate at threshold is much weaker than in quantum wells, being characterized by a T₀ value of about 325 K. Observations of a strong temperature dependence of threshold in quantum dot lasers may have explanations other than Auger recombination, such as recombination from higher lying states, or carrier leakage.     

俄歇复合对应变量子阱激光器阈值电流的影响

通过考虑不同因素对压应变和张应变量子阱激光器阈值电流和特征温度的影响,得到了俄歇复合和非俄歇复合对阈值电流起主要作用的转变温度Tc,小于Tc时,主要是非俄歇复合;大于Tc时,主要是俄歇复合,而且张应变量子阱激光器转变温度要比压应变量子阱激光器的转变温度要高;张应变量子阱激光器与压应变量子阱激光器相比,阈值电流更低,特征温度更高。     

Two-dimensional simulation of constricted-mesa InGaAsP/InPburied-heterostructure lasers

A fully two-dimensional self-consistent numerical model of the steady-state behavior of 1.3 μm constricted-mesa InGaAsP/InP buried-heterostructure lasers is presented. Devices operating at this wavelength are very temperature sensitive and therefore the model for the first time includes coupled solutions to the thermal as well as the electrical and optical equation sets. The temperature dependence is included in the Fermi-Dirac statistics, bandgaps, mobilities, densities of states, Auger recombination coefficients, intervalence band absorption, optical gain, and thermal conductivities. The lasing mode profiles, carrier distributions, threshold currents, and temperature characteristics are analyzed and good agreement is found with experimental results, including the temperature dependence of the threshold current and the prediction of a break-point temperature. The optimum design parameters are investigated for reduced threshold currents, and the effect of optical loss in the blocking regions on lateral-mode control is analyzed     

Band-to-band Auger effect on the output power saturation in InGaAsP LED's

Band-to-band Auger effect on output power saturation in InGaAsP light emitting diodes is studied theoretically. The CHSH-type Auger transition rate is calculated using an approximation formula which involves a weak degeneracy effect. Calculated carrier lifetime and radiance versus current density for 1.3 μm LED's agree with reported experimental results. Band-to-band Auger recombination of the CHSH process greatly affects the radiance saturation in InGaAsP LED's.     

Temperature dependence of the threshold current of QW lasers

The temperature dependence of the threshold current in GaInAs-based laser structures has been studied in a wide temperature range (4.2 ≤ T ≤ 290 K). It is shown that this dependence is monotonic in the entire temperature interval studied. Theoretical expressions for the threshold carrier density are derived and it is demonstrated that this density depends on temperature linearly. It is shown that the main contribution to the threshold current comes from monomolecular (Shockley-Read) recombination at low temperatures. At T > 77 K, the threshold current is determined by radiative recombination. At higher temperatures, close to room temperature, Auger recombination also makes a contribution. The threshold current grows with temperature linearly in the case of radiative recombination and in accordance with T ³ in the case of Auger recombination.     

The effect of temperature dependent processes on the performance of1.5-μm compressively strained InGaAs(P) MQW semiconductor diodelasers

We describe measurements of the threshold current I_th and spontaneous emission characteristics of InGaAs (P)-based 1.5-μm compressively strained multiple-quantum-well semiconductor lasers from 90 K to above room temperature. We show that below a break-point temperature, T_B≈130 K, I_th and its temperature dependence are governed by the radiative current. Above this temperature, a thermally activated Auger recombination process becomes the dominant recombination mechanism responsible for both I_th and its temperature sensitivity. At room temperature nonradiative Auger recombination is found to account for approximately 80% of the threshold current in these devices     

Experimental study of Auger recombination, gain, and temperaturesensitivity of 1.5 μm compressively strained semiconductorlasers

The effect of strain on Auger recombination has been studied using the differential carrier lifetime technique in both lattice matched InGaAs-InP and compressively strained quaternary quantum wells. It is found that Auger recombination is reduced in strained devices. The transparency carrier density and differential gain of both lattice matched and strained devices have been obtained by gain and relative intensity noise measurement. A reduction of the transparency carrier density is observed in the strained device. However, no differential gain increase is seen. The temperature sensitivity of the threshold current density of both lattice matched and strained devices has been fully studied. Physical parameters contributing to the temperature sensitivity of the threshold current density have been separately measured, and it is shown that the change in differential gain with temperature is a dominant factor in determining the temperature sensitivity of both lattice matched and strained devices     

Influences of interfacial recombination on oscillation characteristics of InGaAsP/InP DH lasers

This paper presents the influences of interfacial recombination on the oscillation characteristics of InGaAsP/InP DH lasers. The effects of interfacial recombination at the two InP-InGaAsP interfaces, and a theoretical study of the oscillation characteristics such as threshold current density and differential quantum efficiency are discussed and compared with experimental results. The effects of interfacial recombination on the temperature dependence of threshold current are also examined.