We developed a design of a 980 nm laser diode with GaAs waveguide and thin asymmetric barrier layers (ABLs) placed close to both sides of the active region. The use of AlGaAsSb ABL (or alternatively three AlInAs barriers separated by GaAsP spacers of different thicknesses) for blocking electron transport and GaInP ABL for blocking hole transport suppresses parasitic recombination in the waveguide by 99%.

Using numerical simulation, a search is carried out for designs of asymmetric barrier layers (ABLs) for a laser diode having GaAs waveguide and emitting at the wavelength λ = 980 nm. A pair of ABLs, adjoining the active region on both sides, blocks undesired charge carrier flows and suppresses parasitic spontaneous recombination in the waveguide layers. Optimal designs of ABLs based on AlGaAsSb and GaInP for blocking electrons and holes, respectively, are proposed that make it possible to reduce the parasitic recombination current down to less than 1% of the initial value. To suppress electron transport, an alternative structure based on three identical AlInAs barriers is also proposed. The GaAsP spacers separating these barriers from each other have different thicknesses. Due to this, its own set of quasi-bound (resonant) states is formed in each spacer that is different from the neighbor spacer set of states. As a result of this, the resonant tunneling channels are blocked: the parasitic electron flow is reduced by several tens of times in comparison with the case of spacers of equal thickness.

Using numerical simulation, a search is carried out for designs of asymmetric barrier layers (ABLs) for a laser diode having GaAs waveguide and emitting at the wavelength λ = 980 nm. A pair of ABLs, adjoining the active region on both sides, blocks undesired charge carrier flows and suppresses parasitic spontaneous recombination in the waveguide layers. Optimal designs of ABLs based on AlGaAsSb and GaInP for blocking electrons and holes, respectively, are proposed that make it possible to reduce the parasitic recombination current down to less than 1% of the initial value. To suppress electron transport, an alternative structure based on three identical AlInAs barriers is also proposed. The GaAsP spacers separating these barriers from each other have different thicknesses. Due to this, its own set of quasi-bound (resonant) states is formed in each spacer that is different from the neighbor spacer set of states. As a result of this, the resonant tunneling channels are blocked: the parasitic electron flow is reduced by several tens of times in comparison with the case of spacers of equal thickness.

In a laser with asymmetric barrier layers (ABLs) two thin barrier layers adjacent to the active region on both sides are aimed at prevention of bipolar population of the waveguide layers and, accordingly, at suppression of parasitic recombination in them. In the present work, a theoretical model of the laser with ABLs based on rate equations is proposed, which includes unwanted carrier leakage that inevitably occurs in lasers with ABLs implemented in practice. Solutions of the equations for the steady-state mode are obtained. Using an example of a laser based on an InGaAs/GaAs quantum well (lasing wavelength λ = 980 nm) the effect of the leakage through ABLs on device characteristics is studied. The parasitic fluxes suppression ratios C of ABLs that are required for prevention of unwanted impact of waveguide recombination are estimated. For the case under consideration the effect of using ABLs becomes pronounced at the suppression ratios C ≥ 102. To suppress 90% of the parasitic current, C should be equal to 2.3 · 10^4. In the work, we also study the influence of ABLs on the useful fluxes of carriers entering the active region.

In a laser with asymmetric barrier layers (ABLs) two thin barrier layers adjacent to the active region on both sides are intended to prevent bipolar population of the waveguide layers, hence, to suppress parasitic recombination in them. A theoretical model of a laser with ABLs, based on rate equations which acknowledge undesirable carrier leakage inevitable in lasers of this type implemented in practice, is proposed. Solutions to equations are obtained for the steady-state case. By the example of an InGaAs/GaAs quantum-well laser (lasing wavelength λ = 980 nm), the effect of leakages through ABLs on the device characteristics is studied. The parasitic-flux suppression ratios C of ABLs which are required to prevent the adverse effect of waveguide recombination are estimated. In the case at hand, the effect of ABLs becomes appreciable at suppression ratios of C ≥ 102. To suppress 90% of the parasitic current, C should be 2.3 × 104. The effect of ABLs on useful carrier fluxes arriving at the active region is also studied.

We report on direct large signal modulation and the reliability studies of microdisk lasers based on InGaAs/GaAs quantum well-dots. A 23 μm in diameter microlaser exhibits an open eye diagram up to 12.5 Gbit/s and is capable of error-free 10 Gbit/s data transmission at 30°C without temperature stabilization. The ageing tests of a 31 μm in diameter microdisk laser were conducted at room and elevated temperatures during more than 1200 hr. The average rate of the output power degradation was about 25 and 29 nW/hr at 40°C and 60°C, respectively.

A self-consistent model for calculation of threshold and power characteristics of semiconductor quantum well (QW) lasers with asymmetric barrier layers is developed. The model, which is based on a set of rate equations, uses the universal condition of global charge neutrality in the laser structure. The electron and hole densities in the waveguide region and in the QW and density of photons of stimulated emission are calculated. The local neutrality in the QW is shown to be strongly violated, especially at high injection currents. Violation of neutrality in the QW makes the electron and hole densities in the QW dependent on the injection current in the lasing regime — in the structure considered here, the electron density in the QW decreases while the hole density increases with increasing injection current. Under the conditions of ideal functioning of the asymmetric barrier layers, when the electron-hole recombination in the waveguide region is totally suppressed, violation of neutrality in the QW does not practically affect the dependence of the output optical power on the injection current — the quantum efficiency is close to 1 and the light-current characteristic is linear. Violation of neutrality in the QW weakens, however, the temperature-dependence of threshold current and hence makes the characteristic temperature T0 of the laser higher. Физика и техника полупроводников, 2018, том 52, вып. 12

A search for materials suitable for implementation of 1.55 µm Al-free diode lasers based on InP with asymmetric barrier (AB) layers is conducted. It is shown that a very high (over 106) suppression ratio of the parasitic electron flux can be achieved using common III–V alloys for the ABs. Hence placing such ABs in the immediate vicinity of the active region should completely suppress the parasitic recombination in the waveguide. Several optimal AB designs are proposed that are based on one of the following alloys: Al-free GaInPSb, ternary AlInAs, or quaternary AlGaInAs with a low Al-content. As an important and beneficial byproduct of utilization of such ABs, an improvement of majority carrier capture into the active region occurs.

A self-consistent model for calculating the threshold and high-power characteristics of semiconductor quantum well lasers with asymmetric barrier layers is developed. The model, which is based on a system of rate equations, uses the universal condition of global charge neutrality in the laser structure. The electron and hole concentrations in the waveguide region and in the quantum well (QW) and the concentration of photons of stimulated emission are calculated. The local neutrality in the QW is shown to be strongly violated, especially at high injection currents. The violation of neutrality in a QW makes the electron and hole concentrations there dependent on the injection current under lasing conditions: in the structures under consideration, the electron concentration in the QW decreases while the hole concentration increases with increasing injection current. In the case of the ideal functioning of asymmetric barrier layers, when electron–hole recombination in the waveguide region is completely suppressed, the violation of neutrality in the QW has almost no effect on the dependence of the output optical power on the injection current: the quantum efficiency is close to unity and the light–current characteristic is linear. Nevertheless, the violation of neutrality in the QW causes weakening of the temperature dependence of the threshold current and, hence, an increase in the characteristic temperature T0 of the laser.

We study the possibility of realization of the asymmetric barrier layers (ABL) concept in an 808-nm Al-free GaInAsP/InGaP/GaAs semiconductor laser. Two ABLs on both sides of the active region are aimed to suppress the parasitic recombination in the optical confinement layers. It is shown that such ABL-laser can be made fully Al-free having high suppression ratios for parasitic charge carrier flows (60 and 207 times for electrons and holes, respectively, as compared to a conventional SCH heterostructure).

The feasibility of implementation of asymmetric barriers (ABs) made of common materials for completely aluminum-free diode lasers is studied. The ABs adjoining a low-dimensional active region on both sides aim to prevent bipolar population in the waveguide layers and thus to suppress parasitic recombination therein, which in turn would enhance the efficiency and temperature-stability of the device. Our search algorithm for appropriate AB materials relies on the minimization of undesired carrier flow (electrons or holes passing through the active region toward the p- or n-type doped cladding layer, respectively), while maintaining the useful flows of hole and electron injection into the active region. Using an example of an 808-nm GaInAsP laser, it is shown that the n- and p-side ABs can be made, for instance, of GaInPSb and GaInP, respectively. In such a laser, the parasitic recombination flux can be suppressed by a factor of 60 for electrons and 200 for holes. It is found that the contribution of the indirect valleys to the electron flow through the p-side AB can be significant and even decisive in some cases. The contribution of light holes to the transmission through the ABs can also be considerable. The optimal thicknesses of the AB layers are determined and the chemical composition tolerances are estimated for a given flux suppression ratio.