Yorimitsu Nishitani

Self‐aligned structure InGaAsP/InP DH lasers

Self‐aligned structure InGaAsP/InP DH lasers with emission wavelengths near 1.3 μm are studied. A cw threshold of about 100 mA is obtained in these lasers with cavity lengths of about 300 μm at a heat sink temperature of 25 °C. Light output increases linearly with current for outputs of 10 mW per facet and no kinks appear. Fundamental‐transverse and single‐longitudinal mode oscillation, and stable operation of fundamental‐transverse mode against injection current, are achieved. A cw operation up to 72 °C is obtained with a laser.

Direct observation of defects in Si-doped and Ge-doped Ga0.9Al0.1As epitaxial layers by transmission electron microscopy

Abstract Defects in Si-doped and Ge-doped Ga 0.9 Al 0.1 As epitaxial layers are observed and compared by transmission electron microscopy (TEM). Dislocations and stacking faults which originate from the interface are observed in both kinds of epitaxial layers. Faulted loops are locally observed in Ge-doped layers but not observed in Si-doped layers. These loops are extrinsic in character and have Burgers vectors of the type a /3〈111〉. The density of the faulted loops tends to increase with increasing carrier concentration in a range of 1 × 10 17 − 9 × 10 18 cm −3 .

Etch pits and dislocations of Ga1−xAlxAs liquid phase epitaxial layers

The etch pits of Ga1−xAlxAs are revealed by the etchant (H2O/H2O2/CH3COOH/HF) and it is verified that these etch pits correspond faithfully to dislocations using x‐ray transmission topographs. The shapes of dislocation etch pits which are revealed by the etchant (1 H2O/1 H2O2/2 CH3COOH/0.5 HF) are either conical on the (100) face of Ga1−xAlxAs with x≳0.1 or pyramidal on the (100) face of Ga1−xAlxAs with x=0.05.

Reduction of the Dislocation Density in GaAs1 − x Sb x Layer on GaAs Grown by an Improved LPE Method

An improved LPE method in which the solid surface is always covered by a solution during step‐graded growth of on substrates produces etch pit densities of . In contrast, layers grown by conventional step or continuously graded LPE have EPD of . The composition of the top layer is approximately in all cases. The reduction of EPD by the improved LPE method is attributed to limiting the nucleation of small islands to the first buffer layer, under the conditions that the grown surface is always covered by the solution subsequent to the growth of the first buffer layer.

Deformation of V-grooves on InP substrate by heat treatment

Abstract We found that V-grooves formed by chemical etching along the 〈011〉 direction on InP substrates were deformed by heat treatment in hydrogen. This deformation occurs because of simultaneous etching at the shoulders and deposition at the bottom in the V-groove. This deformation requires the presence of the following: hydrogen gas, phosphorus pressure, and chemical residuals. The activation energy of the deformation was 1 eV between 550 and 710°C. These results lead us to the conclusion that the deformation is caused by the chemical reaction of InP with chemical residuals in hydrogen.

New heterojunction InGaAsP/InP laser with high‐temperature stability (T0 = 180 K)

This letter proposes and demonstrates the operation of a new heterojunction InGaAsP/InP laser, a double‐carrier‐confinement heterojunction (DCC‐heterojunction) laser. This laser is fabricated by incorporating a p‐InGaAsP second well layer into a p‐InP clad layer of the conventional InGaAsP/InP double‐heterojunction laser. With this laser, excellent temperature stability of threshold current [T0 is 180 K in the temperature range of 20–100 °C when threshold current varies with exp(T/T0)] and high external differential quantum efficiency (more than 45% at 100 °C) were achieved. Beam divergence perpendicular to the junction plane was also much improved (less than 25°).

The effect of growth temperature and impurity doping on composition of LPE InGaAsP on InP

Abstract In LPE growth of InGaAsP with an energy gap corresponding to about 1.3 μm wavelength on (100)InP substrates, lattice constants and energy gaps are senstive to the growth temperature and the addition of Sn or Cd impurities, but are not influenced by the amount of step-cooling. The lattice mismatch and PL wavelength decrease with increasing growth temperature at rates of 3.4×10 −4 and 6×10 −3 μm ° C −1 , respectively. The change in lattice constant as a result of impurity doping is mainly caused by the change of the distribution coefficients.

An improved LPE growth method for GaAs-Ga1-xAlxAs double heterostructures

Abstract Epitaxial GaAs-Ga 1- x Al x As multilayers are grown by an LPE method in which the solid surface is always covered by a melt during the growth of the various layers. Only the final melt is wiped from the surface. Wafers which have smooth surfaces are obtained with good reproducibility. It is evident that few dislocations and no stacking faults are generated at the interfaces between epitaxial layers and that “meniscus lines” do not exist on each subsurface in the multilayer except on the top surface.

The preparation and properties of In-Ga-As-P batch prepared melts (batch melts)

Abstract In order to improve controllability and reproducibility of composition and thickness of InGaAsP LPE layers, many identical melts (batch melts) are prepared in one batch process. The conditions to prepare batch melts are determined from diffusion analysis. The uniformity between batch melts is determined from LPE layer properties such as lattice matching, photoluminescence peak wavelength, and layer thickness. The results indicate that the batch melts are uniform and that the technique is very useful.

Liquid phase epitaxial growth of InGaAsP on grooved substrates

Abstract The cross-sectional shape of LPE InGaAsP layers in a V-groove on InP substrates has been studied experimentally and theoretically. The shape varies from an arc to a V-shape as the composition goes away from InP. We have shown that this phenomenon can be explained by calculating the free energy. Calculation shows that the shape of the grown layer in the V-groove is determined by the contact angle between its surface and the facet of the groove.