Ming-Chiang Wu

Very low threshold single quantum well graded‐index separate confinement heterostructure InGaAs/InGaAsP lasers grown by chemical beam epitaxy

We have succeeded in preparing 1.5 μm wavelength strained‐layer graded‐index separate confinement heterostructure (GRINSCH) InGaAs/InGaAsP single quantum well (SQW) injection lasers by chemical beam epitaxy (CBE). These lasers have extremely low threshold current density Jth of 170 A/cm2, internal quantum efficiency of 83%, and internal waveguide loss of 3.8 cm−1. To the best of our knowledge, these results represent the best values obtained thus far from long‐wavelength InGaAs/InGaAsP quantum well injection lasers grown by any techniques. However, despite the recent rapid reduction in Jth, the threshold‐temperature dependence remains poor (T0=45 K) even in these very low Jth GRINSCH SQW lasers.

InGaAs/GaAs/InGaP multiple-quantum-well lasers prepared by gas-source molecular beam epitaxy

We report on the first room‐temperature operation of aluminum‐free In0.2Ga0.8As/GaAs/ In0.49Ga0.51P multiple‐quantum‐well lasers grown by gas‐source molecular beam epitaxy. These lasers have low threshold current density Jth of 177 A/cm2, high internal quantum efficiency of 91%, and low internal waveguide loss of 9.1 cm−1. The characteristic temperature T0 is 150 K, which is the highest value ever reported. These results demonstrate that gas‐source molecular beam epitaxy is suitable for growing high‐quality In0.2Ga0.8As/GaAs/In0.49Ga0.51P lasers.

Chemical Beam Epitaxy of GalnP on GaAs(l 00) Substrates and its Application to 0.98/spl mu/m Lasers

Abstract We present results on the growth, doping, and application to lasers of GaInP on GaAs(100) substrates using chemical beam epitaxy (CBE). The growth studies were performed in the substrate temperature range of 490–555°C. We were able to obtain lattice-matching with good surface morphology over the entire substrate range investigated. For a fixed triethylgallium (TEGa) flow, a sharp increase in the trimethylindium (TMIn) flow required to obtain lattice-matching for T sub above 520°C is observed. This can be attributed to an increase in GaP growth rate and a decrease in InP growth rate due to desorption of TMIn species. The p-type and n-type doping of Ga 0.51 In 0.49 P was investigated using diethylzinc (DEZn) and hydrogen sulfide (H 2 S), respectively. It was found that low substrate temperature (≲ 510°C) was necessary to obtain high p-type doping. Separate confinement heterostructure (SCH) lasers with strained In 0.2 Ga 0.8 As/GaAs multiple-quantum-well (MQW) active layers and Ga 0.51 In 0.49 P cladding layers for operation at 0.98 μm were grown. Broad-area lasers show extremely low threshold current densities, J th , of 70 A/cm 2 . Ridge waveguide lasers with 4 μm stripe width have a threshold of 7.8 mA and gave linear CW output powers upto 100 mW. High external quantum efficiency of 0.9 mW/mA and a very low internal waveguide loss of 2.5 cm -1 were obtained from these lasers.

Low‐threshold InGaAs strained‐layer quantum well lasers (λ=0.98 μm) with GaInP cladding layers prepared by chemical beam epitaxy

We report on the InGaAs/GaAs/GaInP strained‐layer quantum well (QW) lasers grown by chemical beam epitaxy (CBE). The single QW broad‐area layers have a very low threshold current density of 70 A/cm2, which is among the lowest value reported for InGaAs/GaAs/GaInP lasers. Ridge‐waveguide lasers emitting at 0.98 μm have a continuous wave (cw) threshold of 7.8 mA for a 500‐μm‐long cavity and a differential quantum efficiency as high as 0.9 mW/mA. Internal quantum efficiency of 0.95 and internal waveguide losses of 2.5 cm−1 were obtained. Linear cw output power of 100 mW was obtained. These results demonstrate that CBE is capable of growing 0.98 μm InGaAs strained‐layer QW lasers having performance similar to the best prepared by other epitaxial growth techniques.

1.3 μm InGaAsP/InP multiquantum well buried heterostructure lasers grown by chemical‐beam epitaxy

High performance InGaAsP/InP multiquantum well (MQW) buried heterostructure lasers emitting around 1.3 μm were prepared for the first time by chemical‐beam epitaxy. At 20 °C, continuous‐wave (cw) threshold currents were 5–8 mA and quantum efficiencies were 0.35–0.45 mW/mA for 250 μm long lasers having one facet ∼85% reflective coated. At 80 °C, the cw threshold currents remained low, 23 mA, quantum efficiency stayed high, 0.22 mW/mA, and output power of ∼10 mW was achieved. cw power output as high as 125 mW was achieved with 750 μm long lasers having AR–HR (∼5%–85%) coatings. Lasers with bulk active were also studied for comparison. Though they also have excellent device performance, in general, they are somewhat inferior to MQW lasers.

1.5 μm wavelength InGaAs/InGaAsP distributed feedback multi‐quantum‐well lasers grown by chemical beam epitaxy

We demonstrated the first successful growth of 1.5 μm strained‐layer InGaAs/InGaAsP multi‐quantum‐well (MQW) distributed feedback (DFB) lasers by chemical beam epitaxy (CBE). In these DFB wafers, a quaternary grating is placed at the bottom of the MQW stack with an InP spacer layer. Studies by transmission electron microscopy show that defect‐free InP regrowth was achieved with no mass transport needed over the grating corrugations before regrowth. With CBE regrowth the shapes of the gratings were well preserved. The InP overlayer also very effectively smoothed out the quaternary surface corrugations resulting in very flat MQW structures. Buried‐heterostructure 6‐QW DFB lasers (250 μm long and as‐cleaved) operated at 1.55 μm with cw threshold currents 10–15 mA and slope efficiencies up to 0.35 mW/mA (both facets). Side‐mode suppression ratios (SMSR) as high as 49 dB was obtained. The laser operated in the same DFB mode with SMSR staying above 40 dB from threshold and throughout the entire current range ev...

Temperature modulation molecular‐beam epitaxy and its application to the growth of periodic index separate confinement heterostructure InGaAs quantum‐well lasers

Solid‐source molecular‐beam epitaxy has been employed to grow periodic index separate confinement heterostructure InGaAs quantum‐well lasers emitting at 980 nm. The 5 μm×750 μm device fabricated using a self‐aligned process has far‐field angles of 10° by 20°, a threshold current of 45 mA, an external differential quantum efficiency of 1.15 mW/mA (90%), and an output power of 620 mW, all measured at room temperature under cw operation. A record high fiber coupling efficiency of 51% has been achieved.

Generation of subpicosecond optical pulses by mode-locking semiconductor lasers with millimeter-wave sources

Subpicosecond transform-limited optical pulses are generated from monolithic colliding pulse mode-locked multiple quantum well lasers at 1.5- mu m wavelength. The 0.95-ps optical pulses are synchronized with a millimeter-wave oscillator up to 40 GHz and have a modulation depth greater than 95%. Using a passive mode-locking technique, 610-femtosecond optical pulses are also generated at a repetition rate as high as 350 GHz without any synchronization sources. This is the highest pulse repetition rate ever reported for semiconductor optoelectronic sources.<<ETX>>