Hydrostatic pressure dependence of recombination mechanisms in GaInNAs, InGaAsP and AlGaInAs 1.3 μm quantum well lasers

Abstract

From measurements of the threshold current and lasing energy as a function of pressure in InGaAsP/InP, AlGaInAs/InP and GaInNAs/GaAs based multiple quantum well lasers we determine the relative importance of the monomolecular, radiative and Auger recombination processes. For the InP based devices, we find that a simple combination of radiative and non-radiative Auger recombination can fully explain the pressure dependence of the threshold current where the threshold carrier density is approximately constant as a function of pressure. For the GaInNAs/GaAs devices we observe a large increase in threshold current with pressure. This we show is due to the interaction of the nitrogen level with the conduction band which gives rise to an increased conduction band effective mass resulting in an increase in threshold carrier density of ~12% over 10 kbar. This large increase in n th increases the monomolecular, radiative and unusually, the Auger recombination current with pressure explaining the large increase in threshold current with pressure.1 Introduction The development of cheap, temperature-insensitive lasers operating around 1.3 µm and 1.55 µm has for many years been the subject of great attention in the optoelectronics community. Due to the recent emergence and increased demand for metro and Cable Television (CATV) applications, research into efficient devices operating at these wavelengths has gained considerable momentum. The development of 1.3 µm lasers has grown relatively in importance as demand continues for short-haul communications links. In addition, semiconductor lasers operating over the range 1.4 µm to 1.5 µm are becoming of interest as laser pump sources for Raman amplifiers. The III-V materials system InGaAs(P)/InP has been successfully used to produce lasers at both 1.3 µm and 1.55 µm. In spite of the commercial success of these devices, they remain far from ideal due to material and structural dependent problems such as Auger recombination, optical losses and carrier leakage [1]. These give rise to both higher than optimum threshold current densities and high temperature sensitivity over the required temperature range of operation, (typically -4 0 °C to +80 °C), requiring complex and expensive temperature control circuitry. Alternative improved materials have been sought after to overcome these problems.

Temperature and pressure dependence of carrier recombination processes in GaAsSb/GaAs quantum well lasers

“…Also shown is the pressure dependence of the radiative current, as determined from the integrated spontaneous emission at threshold (squares). The measured increase in I rad is in reasonable agreement with the ideal QW transparency model where I rad ∝ E g 2 dependence (dash-dot-dot line) [9], where E g is the band gap which is assumed to be equal to the measured lasing energy. However, the pressure dependence of the threshold current is stronger, particularly above 6 kbar.…”

“…The lower rate of increase of I th with pressure dependence compared to the leakage paths may be explained if carrier leakage together with a non-radiative process that decreases with pressure are both present. Auger recombination decreases with increasing pressure and is known to be important in other lasers operating over this wavelength range [9]. We therefore suggest that the non-radiative recombination which dominates I th at room temperature is due to a combination of carrier leakage and Auger recombination.…”

“…Pressure can be used to vary the splitting between the Γ, L or X-minima and can therefore be used to investigate carrier leakage currents. In most laser materials operating at 1.3 µm, Auger recombination dominates, accounting for 50, 30 and 25% of I th in InGaAsP/InP, InGaAlAs/InP and GaInNAs/GaAs QW lasers at room temperature, respectively [9]. Furthermore, the room temperature threshold current of 1.3 µm InAs/GaAs Quantum Dot lasers is dominated by Auger recombination [2].…”

A theoretical comparison of the pressure dependence of the threshold current of phosphorus-, aluminium- and nitrogen-based 1.3 µm lasers

“…Therefore, our results suggest the conclusion of Fehse et al that the band-to-band AR is not the dominant recombination process in N-based lasers. The measured change in normalized threshold current with pressure for the three competing laser devices by Sweeney et al [59] has shown that the threshold current of P-based lasers decreases with pressure whereas the threshold current of the other two increases with pressure, with rapid increments observed for N-based lasers. They have attributed this strong increase with pressure to the increase in n th with increasing pressure as a result of the heavier CB effective mass.…”