Amplified spontaneous emission (ASE) measurements of a quantum-well coupled quantum-dot (QW–QD) laser are investigated in our experimental study. Fabry–Perot ASE spectrum taken below threshold of this device allows the extraction of gain, index of refraction change, and linewidth enhancement factor. Our experimental study includes continuous wave and pulsed measurements. The QW–QD laser consists of an auxiliary QW which assists in carrier collection while tunneling of carriers takes place from the well to the dot region. Our experimental analysis reveals a low linewidth enhancement factor of 0.15 over a flat spectrum for these GaAs–InGaAs–InAs QW–QD lasers.
We investigated the electrical and structural qualities of Mg-doped p-type GaN layers grown under different growth conditions by metalorganic chemical vapor deposition (MOCVD). Lower 300 K free-hole concentrations and rough surfaces were observed by reducing the growth temperature from 1,040 o C to 930 o C. The hole concentration, mobility, and electrical resistivity were improved slightly for Mg-doped GaN layers grown at 930 o C with a lower growth rate, and also an improved surface morphology was observed. In 0.25 Ga 0.75 N/GaN multiple-quantum-well light emitting diodes (LEDs) with p-GaN layers grown under different conditions were also studied. It was found from photoluminescence studies that the optical and structural properties of the multiple quantum wells in the LED structure were improved by reducing the growth temperature of the p-layer due to a reduced detrimental thermal annealing effect of the active region during the GaN:Mg p-layer growth. No significant difference in the photoluminescence intensity depending on the growth time of the p-GaN layer was observed. However, it was also found that the electroluminescence (EL) intensity was higher for LEDs having p-GaN layers with a lower growth rate. Further improvement of the p-GaN layer crystalline and structural quality may be required for the optimization of the EL properties of long-wavelength (;540 nm) green LEDs.
Data are presented showing that, besides the improvement in carrier collection, it is advantageous to locate strain-matching auxiliary InGaAs layers ͓quantum wells ͑QWs͔͒ within tunneling distance of a single-quantum-dot ͑QD͒ layer of an AlGaAs-GaAs-InGaAs-InAs QD heterostructure laser to realize also smaller size QDs of greater density and uniformity. The QD density is changed from 2ϫ10 10 /cm 2 for a 50 Å GaAs coupling barrier ͑QW to QD͒ to 3ϫ10 10 /cm 2 for a 5 Å barrier. The improved QD density and uniformity, as well as improved carrier collection, make possible room-temperature continuous-wave ͑cw͒ QDϩQW laser operation ͑a single InAs QD layer͒ at reasonable diode length ͑ϳ1 mm͒, current density 586 A/cm 2 , and wavelength 1057 nm. The cw 300 K coupled InAs QD and InGaAs QW AlGaAs-GaAs-InGaA-InAs heterostructure lasers are grown by metalorganic chemical vapor deposition.
Coupled InP quantum-dot InGaP quantum well InP-InGaP-In(AlGa)P-InAlP heterostructure diode laser operation Appl. Phys. Lett. 79, 3215 (2001); 10.1063/1.1416158Highly efficient GaInAs/(Al)GaAs quantum-dot lasers based on a single active layer versus 980 nm high-power quantum-well lasers Short-wavelength laser diodes based on AlInAs/AlGaAs self-assembled quantum dots
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