Suppression of Auger recombination effects in compressivelystrained quantum-well lasers

Based on detailed valence band structure, a Monte Carlo analysis of the Auger recombination effects in compressively strained quantum-well diode lasers has been carried out. The recombination current is found to increase with carrier density, but at a rate far less rapidly than the conventional n³-rule has suggested. At moderate carrier densities, the recombination current is also found to decrease exponentially with increasing strain     

Lifetime calculations for Auger recombination in lead-tin-telluride

Calculations of lifetime have been carried out for intervalley Auger processes in PbSnTe. The more generalized treatment, as compared to Emtage's earlier calculations, accounted for 1) nonparabolic dispersion laws, 2) arbitrary statistics, and 3) arbitrary injection level. The lifetime was found to be an order of magnitude larger than the value given by Emtage's formula. As a result, the predicted performance of PbSnTe lasers and infrared detectors may be much better than thought before.     

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.     

Auger recombination in strained quantum wells

A nonthreshold mechanism for Auger recombination of nonequilibrium carriers in quantum wells with strained layers is investigated theoretically. It is shown that the dependence of the Auger recombination rate on the magnitude of the strain and the height of the heterobarriers for electrons and holes can be analyzed only by calculating the overlap integrals between initial and final particle states microscopically. In quantum wells with strained layers the presence of strain affects qualitatively and quantitatively the electron-hole overlap integral. The dependence of the Auger recombination rate on the quantum well parameters, the magnitude of the stress, and temperature are analyzed for heterostructures based on InGaAsP/InP and InGaAlAs/InP. Fiz. Tekh. Poluprovodn. 31, 358–364 (March 1997)     

Auger recombination in long-wavelength strained-layer quantum-wellstructures

A model calculation of Auger recombination in strained-layer InGaAs-InGaAlAs and InGaAs-InGaAsP quantum-well structures is presented as an extension of an empirical Auger theory based on the effective mass approximation. The valence band effective masses around k_∥=0 are calculated by using a six-band Luttinger-Kohn Hamiltonian and the quasi-Fermi levels are determined with a self-consistent Poisson-Schrodinger solver under the effective mass approximation. Three basic Auger processes are considered with the excited carrier being in a bound state of the quantum well, as well as an unbound state. The empirical model includes Fermi statistics as well as a revaluation of the Coulomb interaction overlap integral in the Auger recombination rate. Bound-unbound Auger transitions are proved to be an important nonradiative recombination mechanism in strained-layer quantum-well systems. Our calculations of Auger coefficient are in reasonable agreement with the experimental data     

Auger recombination rate in InGaAsP lasers

For the Auger recombination rate in InGaAsP there is an order of magnitude discrepancy between the measurements by Su et al. and the calculations by Dutta and Nelson, and Sugimura. It is suggested that a major source of this discrepancy is the method used to calculate the overlap integrals. A calculation that supports this suggestion is described.     

Carrier density dependence of Auger recombination

Auger recombination (AR) is usually assumed to depend on the electron density n and the hole density p like n²p (or np²). But, there are deviations from these rules, mainly in degenerate semiconductors. Studying this case the following results were obtained: 1. Normal AR which is only possible in narrow-gap semiconductors goes approximately as np. 2. Phonon-assisted AR which predominates in “normal” gap semiconductors (E_g ≈ 1 eV) has the “usual” density dependence n²p. 3. Second order AR with two Auger electrons goes with (instead of an expected dependence n³p). Moreover, the density dependence may be influenced by the screening of the Coulomb interaction and by the strength of the excitation.     

Evidence of the importance of Auger recombination for InGaAsP lasers

The temperature dependence of Auger recombination in InGaAsP can be described by two regions, one with a slow increase of the Auger coefficient and one with a strong increase. This behaviour is similar to that of the threshold current of an InGaAsP laser. In particular, the slope of the temperature curve of the Auger coefficient changes at T = 255 K, which is exactly the break point temperature of the threshold current. Auger recombination therefore seems to be the most important cause for the temperature dependence of the threshold current in InGaAsP lasers.     

Measurement of Auger recombination in silicon by laser excitation

A new experimental arrangement for the study of Auger recombination in silicon is described and analyzed. A relatively weakly absorbed YAG:Nd laser beam was used for excitation. The decay of the carrier concentration after the injection pulse was studied by measuring the recombination radiation in a direction perpendicular to the laser beam. At some distance from the injection surface the influence of surface recombination and diffusion is then negligible. It has previously been shown that in this geometry the carrier concentration distribution after the laser excitation is accurately described by an analytical expression which accounts for attentuation of the laser beam by both interband and free carrier absorption. Thus the local carrier concentration in the sample can be computed to a high degree of accuracy, which is essential in the determination of the Auger recombination coefficient from decay measurements. Furthermore, this experimental geometry eliminates the problems with laser stray light. Assumptions regarding the influence of surface recombination and diffusion are not necessary in the interpretation of the experiments. The method is usable for silicon in the temperature interval 150–400 K. Preliminary measurements of the Auger coefficient at room temperature are reported.     

俄歇复合对同质结InGaAs探测器探测率的影响

通过对InGaAs材料的俄歇(Auger)复合机制的理论分析,给出了少子寿命与材料组分、温度和载流子浓度的关系,从而得到材料参数等对InGaAs探测器的探测率影响的结果,优化材料参数和器件结构可抑制Auger复合机制,提高InGaAs探测器的探测率.     

Auger and radiative recombination of acceptor bound excitons in semiconductors

We report on a theoretical and experimental study of acceptor bound exciton recombination. We present calculations of phononless Auger and radiative recombination in direct and indirect band gap materials. We consider hydrogenic acceptors in the direct band gap material Hg_1−xCd_xTe in which the band gap can be varied by changing alloy composition. We present calculations of the Auger transition rate and no-phonon oscillator strengths for the common acceptors in Si and Ge. We have measured the bound exciton lifetimes and no-phonon oscillator strengths for the acceptors in Si and find reasonable agreement with the calculated values.     

Experimental comparison of localized and free carrier Auger recombination in silicon

The lifetimes of excitons bound to different shallow impurities in silicon have been measured. A comparison with a theoretical calculation shows that a 3-particle Auger process dominates the recombination. In the case of high carrier concentration the lifetime of free carriers is also governed by the Auger recombination. In contrast to the bound excitons this Auger process cannot be of first order but an additional excitation, probably a phonon, must be involved. It turns out, indeed, that the excitonic Auger recombination is more “effective” than the band-to-band transition, as expected for a lower order process. A comparison of the results for the highly doped material with those for highly excited pure samples (electron-hole drops, EHD) shows that also in this case the Auger recombination dominates.     

Resonance structure of the rate of Auger recombination in silicon nanocrystals

The rate of Auger recombination in silicon nanocrystals is calculated in the context of the approximation of the envelope function. It is shown that the dependence of the rate on the crystallite radius is an essentially unsteadily varying function with characteristic variations within three or four orders of magnitude. The maximum rates of Auger recombination in silicon are reached at certain “resonance” nanocrystal dimensions, such that the energy of the basic interband transition coincides with the energy of some intraband transition.     

Optical line shape functions in quantum-well and quantum-wirestructures

Line shape functions in quantum-well and quantum-wire structures are theoretically analyzed taking non-Markovian relaxation processes into account. For high carrier density (as in laser operation), the line shape functions in low-dimensional systems have a strong convergent characteristic because the carrier-carrier coupling, i.e. the system-reservoir coupling, becomes stronger in the lower-dimensional systems. In particular, the line shape of the quantum wire can be approximated by the Gaussian function. In the case of low carrier density, the lower-dimensional systems have smaller homogeneous broadening widths because of longitudinal optical phonon localization; the transverse relaxation times are 0.1 ps (bulk), 0.3 ps (quantum well), and 0.7 ps (quantum wire)     

A suppression mechanism of Auger recombination effects in strainedquantum wells induced by local negative curvature of the energy bandstructure

An analytical method has been developed to calculate distribution of carriers that undergo CHHS Auger recombinations in semiconductors. From this approach, it is further discovered that holes with a local negative effective mass are, statistically, not favored in the CHHS Auger recombination process. As extended regions in valence subbands of compressively strained quantum well structures possess a negative curvature-and thus a local negative hole effective mass-this mechanism is identified to be a significant factor that suppresses Auger recombination effects in compressively strained quantum well laser diodes. This suppression mechanism is also observed and confirmed by recent Monte Carlo calculation results     

Surface-recombination-free InGaAs/InP HBTs and the base contact recombination

Surface-recombination-free InGaAs/InP HBTs with graded base have been demonstrated. The HBTs were passivated by ammonium sulfide. The current gain of the nonself-aligned HBTs was independent of the emitter periphery, indicating that the surface recombination was removed by the passivation. For the self-aligned HBTs, the current gain was still dependent on the emitter periphery after the passivation due to the base contact recombination. A surface leakage channel has been identified to result in a significant increase in the base contact recombination. The passivation has two effects: one is the surface recombination velocity reduction and the other is the surface leakage channel elimination.     

Influence of temperature on Auger recombination lifetime in In1?xGaxAs materials

The influence of temperature and Ga composition on Auger recombination lifetime in n-type and p-type In1-xGaxAs materials is investigated through the simulation, assuming the concentrations of electrons and holes are 1017 cm-3 and 1018 cm-3, respectively. The results show that the temperature has little influence on Auger recombination lifetime of In1-xGaxAs materials at x<0.3. However, it has a great impact when x>0.3 and the effect is more obvious at a lower temperature. Moreover, Auger ...     

Numerical simulation of a forward-biased p-i-n structure with band-to-band Auger recombination

A modification of the iterative scheme of Seidman and Choo is described. The proposed method is suited for the modelling of processes in semiconductor structures including Auger recombination. Some results of calculations are given.     

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.     

Comparison of Auger recombination in GaInAs-AlInAs multiple quantum well structure and in bulk GaInAs

Carrier lifetime has been measured in GaInAs-AlInAs multiple quantum well structures and in thick GaInAs samples for local carrier densities between2 times 10^{17}and5 times 10^{19}cm^-3. Carrier lifetime and Auger recombination are found to be very close (±20 percent) in the two structures. The Auger limited T0values calculated for DH and MQW lasers are found to be, respectively, 93 and 170 K. Optimization of the quantum well laser as a function of the number of wells in the active region is discussed.