Teruhito Matsui

1.5 μm GaInAsP/InP buried‐heterostructure laser diode fabricated by reactive ion etching using a mixture of ethane and hydrogen

A 1.5 μm GaInAsP/InP buried‐heterostructure laser diode was fabricated by reactive ion etching using a mixture of ethane and hydrogen for the formation of mesa stripe. Blocking layers were regrown on the dry etched wafers by liquid phase epitaxy. Continuous‐wave operation was obtained at room temperature. A threshold current as low as 15 mA was achieved, which is superior to that of the same structure laser diode fabricated by conventional chemical etching.

Emission spectra of single quantum well lasers with inhomogeneous current injection

Emission spectra of a tandem‐type GaAs single quantum well laser diode were investigated under pulsed operating conditions. By controlling the two injection current levels, we could force the device to operate not only at the lowest (n=1) quantized state transition but also at the second (n=2) transition. Anomalous pulse responses, moreover, were found for the two lasing modes which were simultaneously observed in time‐integrated spectra. The dynamic emission behavior was utilized to achieve a variety of intensity combinations of the two radiation modes at the widely different wavelengths.

GaInAsP/InP lasers with etched mirrors by reactive ion etching using a mixture of ethane and hydrogen

A reactive ion etching method is applied to fabricate mirrors of 1.5 μm GaInAsP/InP mass transport lasers using a mixture of ethane and hydrogen as an etchant. Threshold currents as low as 35 mA are achieved for the 300‐μm‐long cavity lasers with one etched and one cleaved facet. The differential quantum efficiencies of the lasers with one dry etched facet and both dry etched facets are 13 and 9.5%, respectively.

Photoluminescence characterization of InP surface reactive ion etched by a gas mixture of ethane and hydrogen

InP crystals were etched by reactive ion etching (RIE) with gas mixture of ethane and hydrogen (C2H6/H2), and etching damages were characterized by photoluminescence (PL) measurements of near‐edge and defect‐related emissions. Near‐edge PL emission intensities after RIE were equal to or larger than those before RIE, except for the samples etched for 50 min. The damage introduced by RIE was restricted to the very‐near‐surface region which can be removed by HF treatment. The peak energy of defect‐related 1.1‐eV deep emission bands shifted toward the lower‐energy side for the crystals with etching damages at the surface. The peak shift is attributable to the increase of defect complexes such as P‐vacancy–P‐interstitial or P‐vacancy–In‐vacancy.

Optical switch for multimode optical-fiber systems

A new type of optical switch is constructed of graded-index rod lenses. It is operated mechanically by small electromagnets. This switch is compatible with practical multimode-fiber communication systems. It has many outstanding features, such as low insertion loss (1.3–1.4 dB), low crosstalk ( 2 × 106 times), and small size (40 × 50 × 25 mm3).

Dual‐wavelength emission from a twin‐stripe single quantum well laser

We demonstrate a dual‐wavelength laser constructed from a single quantum well structure. The device includes twin‐stripe waveguides which differ in width. The two constituent emitters in the device of appropriate cavity lengths operate at widely different wavelengths, which are based on the lowest (n=1) and the second (n=2) quantized state transitions. Lasing behavior is interpreted in terms of the difference of the internal cavity loss of the waveguides.

High-purity In0.53Ga0.47As layer grown by liquid phase epitaxy

Abstract High-purity InGaAs epitaxial layers with an area of 15 × 30 mm 2 were grown by using a conventional leak-tight liquid phase epitaxial growth system without any special treatments. A room temperature electron mobility as high as 12000 cm 2 V -1 s -1 and an electron concentration as low as (1−2) × 10 15 cm -3 were reproducibly achieved merely by baking the growth solution in hydrogen.

Lasing wavelength of an asymmetric double quantum well laser diode

It is demonstrated that in an asymmetric coupled GaAs double quantum well structure, we are able to choose a lasing wavelength out of at least four quantum state transitions by cavity loss control. The assignments of the observed lasing transitions are determined by photoluminescence measurement for the laser wafer, as well as by calculations using an isolated potential well model. We propose that one can realize wide‐range wavelength tuning and multistep wavelength switching functions by modifying the two‐dimensional density of states.

Role of carbon and hydrogen in reactive ion etching of InP by gas mixture of ethane and hydrogen

InP crystals were etched by reactive ion etching (RIE) with ethane and hydrogen (C2H6/H2). Etched crystals and gas species were characterized by photoluminescence and mass spectroscopic measurements. Evaporation of phosphorus is induced by hydrogen, mainly originating from H2 gas. Incorporation of C increases with the gas species of hydrocarbon having multiple bonds. Near-bandgap emission with intensities greater than before RIE, which shows the hydrogen passivation, and defect-complex-related emission bands at 1.06-1.07 eV enhanced by RIE were observed. The role of gas species and the identification of defects are discussed on the basis of the experimental results.

Diffusion mechanism of Cd in InP and InGaAs

Cadmium was diffused into InP and InGaAs using Cd3P2 + P or Cd3P2 + Cd3As2 as the diffusion sources. Two diffusion fronts were observed. The diffusion characteristics for Cd3P2 + P sources are interpreted based on the interstitial-substitutional model, or its modification, the vacancy complex model. The charge state of the diffusing interstitial cadmium atom is a singly ionized donor. The chemical species of phosphorus which reacts with InP is P2 and gaseous Cd originates from solid-phase CdP2. For Cd3P2 + Cd3As2 diffusion sources, the effective diffusion coefficient and the surface acceptor concentration decrease with increasing the Cd3As2 weight fraction. The relative depth of the deeper diffusion front becomes more deep when the supply of vacancies is suppressed.