Dietmar Schlenker

Lasing Characteristics of Low-Threshold GaInNAs Lasers Grown by Metalorganic Chemical Vapor Deposition

We report on the lasing characteristics of low-threshold long-wavelength GaInNAs double quantum well (DQW) lasers grown by metalorganic chemical vapor deposition (MOCVD). We have achieved a threshold current density of 450 A/cm2 for a 1.28-µm-emitting laser. This is the lowest value for 1.3-µm-range GaInNAs lasers grown by MOCVD. We also observed high characteristic temperatures (T0) of 210 K and 130 K for 1.25 µm and 1.28 µm lasers, respectively. In addition, we investigated the gradual change in lasing characteristics under pulsed operation. The blue shift of an emission wavelength and a threshold current reduction were observed, which is similar to that observed in the thermal annealing of GaInNAs.

Growth of highly strained GaInAs/GaAs quantum wells for 1.2 μm wavelength lasers

In this paper we present a successful growth of highly strained GaInAs/GaAs quantum wells by low-pressure organometallic vapor-phase epitaxy using tertiarybutylarsine. The transition from uniform to island or dot-like growth mode has been prohibited by carefully choosing the growth condition. Photoluminescence wavelengths of up to 1.2 μm with a FWHM of 23 meV were obtained. We experimentally determined the maximum well thickness for highly strained GaInAs/GaAs QW of good crystal quality and compared our results to critical thickness models. Transmission electron microscopy measurements were used to discuss the degradation mechanism for highly strained GaInAs layers. Also excellent lasing properties of 1.2 μm highly strained GaInAs/GaAs quantum well lasers have been demonstrated.

CBE and MOCVD growth of GaInNAs

We have investigated growth of GaInNAs by MOCVD using dimethylhydrazine (DMHy) and by CBE using RF-radical nitrogen. It was found that there was a large difference in nitrogen incorporation characteristics between the two growth methods. Nitrogen composition of MOCVD increased with a superlinear characteristic against nitrogen source flow and indium composition enhanced such a characteristic. CBE showed a linear incorporation characteristic of nitrogen composition due to the strong reactivity of nitrogen atoms. Photoluminescence intensity was decreased by increasing emission wavelength for both growth techniques, however, the degradation behavior seemed to depend on the nitrogen incorporation characteristic. The hydrogen and carbon concentration of MOCVD grown sample was more than ten times larger than that of CBE grown samples. The comparison of growth characteristics and material qualities may provide useful information for improving the GaInNAs crystal quality.

1.17-μm highly strained GaInAs-GaAs quantum-well laser

Excellent lasing properties and temperature characteristic of a highly strained 1.17-/spl mu/m GaInAs-GaAs double-quantum-well laser are reported. We show that a strained buffer layer, which is employed in the device, has no tradeoff on the device performance. For a 1500-/spl mu/m-long laser with cleaved facets a threshold current density of 200 A/cm/sup 2/ is achieved. A transparency current density of 180 A/cm/sup 2/ is estimated for as cleaved devices. A record high characteristic temperature in this wavelength range of 150 K is achieved.

Low temperature growth of GaInNAs/GaAs quantum wells by metalorganic chemical vapor deposition using tertiarybutylarsine

The low temperature growth of highly strained GaInNAs/GaAs quantum wells was investigated by low-pressure metalorganic chemical vapor deposition (MOCVD) using tertiarybutylarsine (TBAs) and dimethylhydrazine. We found that the incorporation behavior of indium in the strained GaInAs layers at low growth temperature was very different from that at high growth temperature. The N content dropped rapidly with increasing In content in the strained GaInNAs layer. It is pointed out that the V/III ratio is an important growth parameter for TBAs based MOCVD. The V/III ratio strongly affected both the photoluminescence intensity and the alloy composition of the GaInNAs.

Miscibility gap calculation for Ga1−xInxNyAs1−y including strain effects

Abstract A method including strain effects is introduced for calculating the miscibility gap of the GaxIn1−xNyAs1−y material system. The Gibbs free energy is computed using the delta lattice parameter model and the conventional solution model. The contribution caused by the strain energy due to the mismatch between substrate and epitaxial layer is added. The spinodal points can be calculated from this expression. The critical temperature above which the solid is metastable has been found to be increased due to strain effects. It is pointed out that the result of the calculation depends on the choice of substrate. The miscibility gaps for GaxIn1−xAs, GaNyAs1−y and GaxIn1−xNyAs1−y are evaluated by this method for a more realistic model of crystal growth.

Lasing Characteristics of 1.2 µm Highly Strained GaInAs/GaAs Quantum Well Lasers

In this study, we demonstrate a highly strained 1.2 µm GaInAs/GaAs quantum well laser which may be used in high-speed local area networks. Edge emitting lasers with either a GaInP or AlGaAs cladding layer have been fabricated. We have achieved a threshold current density as low as 170 A/cm2 for GaInP-cladding-layer lasers and a high characteristic temperature T0 as high as 211 K from 30°C to 120°C for AlGaAs-cladding-layer lasers. The material gain coefficient g0 was estimated to be 1550 cm-1 which is comparable to that of 0.98 µm GaInAs lasers. A preliminary lifetime test under heatsink-free CW condition was carried out, which shows no notable degradation after 300 h. We also demonstrated an AlAs oxide confinement laser in a 1.2 µm wavelength band.

Quality Improvement of GaInNAs/GaAs Quantum Well Growth by Metalorganic Chemical Vapor Deposition Using Tertiarybutylarsine

A highly strained GaInNAs/GaAs quantum well (QW) was investigated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) using tertiarybutylarsine (TBAs) and dimethylhydrazine. The V/III ratio was found to be an important parameter especially for highly strained QW growth using TBAs based on MOCVD. The optimum V/III ratio window of GaInNAs/GaAs QW growth was very narrow and located at different temperatures and In contents. We propose a postgrowth annealing procedure for improving the quality of GaInNAs/GaAs QW. The photoluminescence intensity was significantly improved after annealing at 640°C.

Data transmission over single-mode fiber by using 1.2-μm uncooled GaInAs-GaAs laser for Gb/s local area network

We demonstrate 2-Gb/s data transmission through a 5-km-long standard single-mode fiber by using a GaAs-based 1.2-/spl mu/m GaInAs-GaAs quantum well laser. The fabricated laser exhibits a high characteristic temperature of 140 K. The results indicate the possibility of Gigabit/s local area networks (LANs) using uncooled lasers (possibly surface-emitting lasers) operating at a 1.2-/spl mu/m wavelength band.

Critical layer thickness of 1.2-μm highly strained GaInAs/GaAs quantum wells

In this paper we experimentally determined the critical layer thickness for highly strained 1.2-μm GaInAs/GaAs quantum wells of good crystal quality. The dependence of the critical layer thickness on the indium content indicates that the observed quality degradation is caused by a growth mode transition. This is also supported by transmission electron microscopy measurements. We discuss the possibility of extending the wavelength of highly strained GaInAs/GaAs quantum wells toward 1.3 μm by delaying the growth mode transition. As a first step, a wavelength extension to 1.225 μm is achieved by using the presented technique.