Optimization of type-II heterostructures for the tuning region in tunable laser diodes

Abstract

Type-II superlattices are very attractive as tuning regions in tunable laser diodes exploiting the free-carrier plasma effect. Due to the confining of the electrons and holes in different layers, the recombination of the electron-hole pairs is drastically suppressed. As a result, the carrier density, and hence the tuning efficiency for type-II superlattices, is enhanced by more than an order of magnitude in the small current regime as compared to bulk tuning regions. However, with increasing carrier density the recombination rate increases because of the stronger penetration of the electron and hole wavefunctions into the corresponding barriers. For high carrier densities, the capability of type-II superlattices depends critically on design parameters such as as layer thickness, band offset and strain. Our calculations show that, for an optimized type-II superlattice, the tuning range can be significantly enhanced by more than a factor of 3 for a given current.

On the design and analysis of AlInAs/AlGaInAs/AlGaAsSb type-II heterostructures for telecommunication applications

“…AlGaAsSb. The unusually high values of band offsets are common for these quaternaries and the results presented here are in general agreement with those analysed in [6].…”

“…Very recently the use of optimised type-II superlattices has been proposed for the tuning region in tunable laser diodes exploiting the free-carrier plasma effect. This showed an enhancement in the tuning range by a factor of 3 when compared with a tuning region containing bulk materials [6]. In addition, type-II and "W" lasers based on the dilute nitride material system have been proposed and analysed for GaAs-based lasers at 1.55 µm [7,8].…”

Growth of various antimony-containing alloys by MOVPE

“…First mirror-like layers were grown with TMGa, TMIn, PH 3 and TMSb at a substrate temperature of 575 1C, which is the highest usually used growth temperature for GaInAsSb and not too far away from the optimal temperature of 650 1C for GaInAsP layers. By attempting to reach gallium-and antimony-rich compositions an increasing group V incorporation coefficient C V was recognized by XRD and PL measurements, assuming a constant group III incorporation coefficient C III taken from a lattice-matched GaInAs layer grown at 575 1C.…”

“…Besides the low bandgap, antimonides feature a type-II band alignment, which is utilized for ''W''-shaped quantum wells [2], but offer also an important improvement for electrical tunable lasers based on the plasma effect [3]. Such InP-based devices are essential components for various telecommunication applications and have received considerable attention in recent years [4].…”