GaInN/GaN Multi-Quantum Well Laser Diodes Grown by Low-Pressure Metalorganic Chemical Vapor Deposition
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Internet Journal Nitride Semiconductor Research
GaInN/GaN Multi-Quantum Well Laser Diodes Grown by Low-Pressure Metalorganic Chemical Vapor Deposition P. Kung1, A. Saxler12, D. Walker1, A. Rybaltowski1, Xiaolong Zhang 1, J. Diaz1 and M. Razeghi1 1Center for Quantum Devices, Department of Electrical and Computer Engineering, Northwestern University, 2Air
Force Research Laboratory, Materials Directorate, Wright-Patterson AFB,
(Received Wednesday, December 31, 1997; accepted Wednesday, January 14, 1998)
We report the growth, fabrication and characterization of GaInN/GaN multi-quantum well lasers grown on (00·1) sapphire substrates by low pressure metalorganic chemical vapor deposition. The threshold current density of a 1800 µm long cavity length laser was 1.4 kA/cm2 with a threshold voltage of 25 V. These lasers exhibited series resistances of 13 and 14 Ω at 300 and 79 K, respectively.
1
Introduction
Semiconductor laser diodes (LDs) and light emitting diodes (LEDs) emitting in the ultraviolet-to-visible spectral region are important sources of light for practical applications. Of particular importance is the use of short wavelength (λ~400 nm) laser diodes for the optical data storage (compact disk, digital video disk), printing and imaging industry. At present, only a few research groups have reported III-V nitride based laser diodes. [1] [2] [3] [4] [5] [6] In this paper, we report the growth, fabrication and characterization of GaInN/GaN multi-quantum well laser diodes emitting at 405 nm. 2
GaInN/GaN multi-quantum wells
The epitaxial layers were grown on (00·1) sapphire substrates by low pressure metalorganic chemical vapor deposition (LP-MOCVD). Details of the growth conditions may be found in Ref. [7]. Figure 1 shows the room temperature photoluminescence and optical pumping from a 10 period 33Å Ga0.89In0.11N/66Å GaN multiple quantum well (MQW) structure capped with a thin GaN layer. The photoluminescence measurements were conducted using a 10 mW He-Cd laser. The optical pumping was carried out using a pulsed nitrogen laser (337 nm) with a pulse width of 600 ps and a repetition rate of 6 Hz. Neutral density filters were used to attenuate the optical power. Stimulated emission was collected from a bar with mechanically polished edges and was observed for pumping densities higher than a threshold estimated at 100 kW/cm2. The peak position
was 401 nm and its width of ~1 nm was limited by the resolution of the measurement equipment. 3
GaInN/GaN multi-quantum well lasers
Figure 2(a) shows a schematic diagram of the laser diodes grown under the same conditions as discussed in the previous section, which consisted of (i) a 3 µm-thick Si-doped GaN (n~ 2x1018 cm-3); (ii) a 10 period 33 Å Ga0.89In0.11N/66 Å GaN multiple quantum wells; and (iii) a 0.25 µm-thick Mg-doped GaN contact layer (p~2x1017cm-3). The wafers were then annealed using rapid thermal annealing (RTA) under nitrogen ambient for 30 seconds at 1000° C to achieve low resistivity ptype GaN:Mg [8], and broad-area lasers with 100-µm wide stripes were
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