Manabu Mitsuhara

Metalorganic molecular beam epitaxy of strained InAsPInGaAsP multi-quantum-wells for 1.3 μm wavelength laser diodes

This paper describes the growth of both InAsP single layers and InAsPInGaAsP multi-quantum-well (MQW) structures by metalorganic molecular beam epitaxy (MOMBE). The AsP ratio in the InAsyP1−y films is proportional to the ratio of the AsH3PH3 supply sources. The well-number dependence of the MQWs is characterized by X-ray analysis, photoluminescence (PL), and transmission electron microscopy, revealing that the critical thickness of InAs0.5P0.5 is approximately 70 nm at 520°C. The PL spectrum of an MQW with 8 nm thick InAsP well layers has a full width at half maximum (FWHM) of 4.1 meV at 4 K. The MQW lasers have a threshold current density of 0.74 kA/cm2 with a cavity length of 300 μm. The maximum operating temperature is as high as 145°C for a 10-well MQW laser with cleaved facets.

2.33-

We demonstrate 2.33-mum-wavelength InP-based distributed feedback (DFB) lasers with InAs-In0.53Ga0.47 multiple-quantum wells as the active region. The maximum output power is 20 mW at 25degC and the maximum operating temperature is as high as 95degC. Stable single-mode operation with a sidemode suppression ratio of 30 dB is obtained, and the emission wavelength of the laser is finely controlled from 2.335 to 2.348 mum by adjusting the injection current and the operating temperature. The current-tuning and temperature-tuning rates of the DFB wavelength are +0.007 nm/mA and +0.148 nm/K, respectively.

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Single-mode operation beyond 2.05-/spl mu/m wavelength has been achieved in InGaAs-InGaAs distributed-feedback (DFB) laser with four quantum wells. The continuous-wave output power is 10.5 mW at a drive current of 200 mA and 25/spl deg/C, The tuning range of the wavelength is between 2.051-2.056 /spl mu/m with a temperature tuning rate of +0.125 nm//spl deg/C.

m-Wavelength Distributed Feedback Lasers With InAs–In

We report on the effect of antimony surfactant on the growth of strained InGaAs multiple-quantum-well (MQW) structure by metalorganic vapor phase epitaxy and the application of the structure to buried-heterostructure (BH) lasers. For a 1.85%-strained MQW, supplying a small amount of antimony during well growth is effective in suppressing the three-dimensional growth and increasing the photoluminescence peak intensity at a wavelength of 2.09 μ m . The secondary ion mass spectroscopy measurement reveals that hardly any antimony is incorporated into the wells. The fabricated BH laser has an emission wavelength of 2.103 μ m under continuous-wave operation at 25 °C.

_{0.53}

Device quality InAs/InGaAs multiple quantum well (MQW) structures were grown on InP substrates by metalorganic vapor phase epitaxy (MOVPE) and applied to lasers emitting at wavelengths longer than 2 mum. InAs/InGaAs MQWs with flat interfaces were obtained by adjusting the growth temperature between 460 degC and 510 degC. The photoluminescence peak wavelength of the MQWs increases from 1.93 to 2.47 mum as the thickness of InAs quantum wells increases from 2 to 7 nm. The structural and optical properties remained almost unchanged even after annealing at 620 degC. For 40-mu m-wide stripe broad-area lasers with 5-nm-thick InAs quantum wells, a lasing wavelength longer than 2.3 mum and an output power higher than 10 mW were achieved under continuous-wave operation at a temperature of 25 degC. These results indicate that InAs/InGaAs MQW structures grown by MOVPE are very useful for the active region of 2 mum wavelength lasers.

Ga

We report the growth of a four-period multiple quantum well (MQW) structure with 115-A-thick, +1.65% strained wells by metalorganic molecular beam epitaxy and its application to 2 μm wavelength lasers. Transmission electron microscopy and photoluminescence measurements reveal that the structural and optical properties of MQW are sensitive to the barrier strain: the values of barrier strain required for MQW with both flat barrier-well interfaces and strong photoluminescence fall within a small range from −0.17% to +0.14%. The double-crystal x-ray diffraction pattern of the MQW remains unchanged before and after annealing at 620 °C for 2.5 h. Buried heterostructure lasers fabricated using metalorganic vapor phase epitaxy regrowth have an emission wavelength of 2.07 μm under a continuous operation current of 120 mA at 55 °C.

_{0.47}

We examined the critical thickness of strained multi quantum wells (MQWs) consisting of InAsP/InGaAsP and InGaAsP/InGaAsP. More than 50 MQWs with different total thicknesses, well strain, and well thicknesses were prepared by metalorganic molecular beam epitaxy (MOMBE) or metalorganic vapor phase epitaxy (MOVPE) to study the influence of net strain, strain type, and temperature on critical thickness. The microscopic photoluminescence method was used mainly to observe misfit dislocations in the MQWs. Three kinds of net strain-critical thickness curves were experimentally determined, i.e., the curves for compressive as well as tensile strained MQWs grown by MOMBE and that for compressive strained MQWs grown by MOVPE. We found that the above three curves coincide with each other and differ greatly from the Matthews’ [J. W. Matthews and A. E. Blakeslee, J. Cryst. Growth 27, 118 (1974)] theoretical curve in a low-net strain range of less than 0.5%.

As Multiple-Quantum Wells on InP Substrates

Strain‐compensated InAsP/InGaAsP multi‐quantum‐wells (MQWs) grown by metalorganic molecular beam epitaxy (MOMBE) are characterized by conventional photoluminescence (PL), micro‐PL, transmission electron microscopy, and x‐ray diffraction measurements and applied to fabricate 1.3 μm wavelength laser diodes. These methods reveal that there is no deterioration in the optical properties or structure of strain‐compensated MQWs having up to 25 wells, which means that the critical thickness of InAsP grown by MOMBE exceeds 1000 A. The critical conditions of strain and thickness over which misfit dislocations are generated are determined for the MQWs. The MQW lasers with ten wells (Lz=55 A) have no misfit dislocations and have uniform threshold current densities of 0.9±0.1 kA/cm2. The maximum operating temperature Tmax of the lasers increases with increasing well number, the highest Tmax is 155 °C, which is obtained for MQW lasers with 15 wells. The lasers have no problems in terms of long‐term reliability.

2.05-μm wavelength InGaAs-InGaAs distributed-feedback multiquantum-well lasers with 10-mW output power

Abstract We have investigated the effect of the barrier strain in +1.65%-strained In 0.77 Ga 0.23 As/InGaAs multiple quantum wells (MQWs) on the structural and optical properties by means of double-crystal X-ray diffraction, transmission electron microscopy (TEM), and room-temperature photoluminescence (PL). The optimum condition of the barrier layer deduced from the X-ray and the PL measurements was nearly lattice-matching, i.e., strain from −0.40 to +0.20% is required for the sharp X-ray diffraction satellite peaks and from −0.17 to +0.14% for large PL intensity. Under compressive strain in the barrier layer, misfit dislocations are introduced into the MQW structures. In the case of tensile strain, however, threading dislocations originating from the thickness undulations in the wells and the barriers are observed. The TEM studies reveal that the thickness undulations are induced by the compositional modulation. The undulation and modulation are enhanced by increasing the tensile strain in the barrier layers. These results indicate that the strain-compensation does not work well on the MQW containing such highly strained InGaAs wells.

Surfactant-mediated growth of InGaAs multiple-quantum-well lasers emitting at 2.1μm by metalorganic vapor phase epitaxy

We have investigated InGaN/GaN multiple quantum well (MQW) solar cells in terms of the relationship between the short-circuit current and the MQW structure. We previously reported that higher short-circuit current is obtained in solar cells with thinner GaN barrier layers, and in this investigation, we also obtained higher short-circuit current in solar cells with higher numbers of InGaN/GaN periodic layers. These results can be explained by the hypothesis that the transport characteristics of photoinduced carriers are characterized by the specific length within which carriers photoinduced in the InGaN well layer can move before recombination. The carrier collection efficiency is improved by the drift in the barrier layer due to the forward internal electric field and degraded by the carrier accumulation in the well layer caused by the inverse internal electric field and the potential barrier between layers, which well describes the influence of the MQW structure on the specific length. Using this model, we discuss how we can determine the MQW structure that yields higher short-circuit current, and conclude that the optimum thickness of the InGaN well layer is about 2–3 nm when the thickness of the GaN barrier layer is 3–8 nm.