We demonstrate the lateral optical confinement of GaN-based vertical-cavity surface-emitting lasers (GaN-VCSELs) with a cavity containing a curved mirror that is formed monolithically on a GaN wafer. The output wavelength of the devices is 441–455 nm. The threshold current is 40 mA (Jth = 141 kA/cm2) under pulsed current injection (Wp = 100 ns; duty = 0.2%) at room temperature. We confirm the lateral optical confinement by recording near-field images and investigating the dependence of threshold current on aperture size. The beam profile can be fitted with a Gaussian having a theoretical standard deviation of σ = 0.723 µm, which is significantly smaller than previously reported values for GaN-VCSELs with plane mirrors. Lateral optical confinement with this structure theoretically allows aperture miniaturization to the diffraction limit, resulting in threshold currents far lower than sub-milliamperes. The proposed structure enabled GaN-based VCSELs to be constructed with cavities as long as 28.3 µm, which greatly simplifies the fabrication process owing to longitudinal mode spacings of less than a few nanometers and should help the implementation of these devices in practice.

Boron ion implantation, which is used for confining carriers in gallium nitride (GaN)-based vertical-cavity surface-emitting laser diodes (VCSELs), was studied. Detailed analysis indicated that boron ion implantation of GaN increases GaN’s absorption coefficient from zero to 800 cm−1 and its refractive index from 2.45 to 2.51 at the surface of the wafer at a wavelength of 453 nm. The depth profile of boron obtained by secondary ion mass spectroscopy (SIMS) showed an exponential decrease toward the bottom of the wafer. Assuming that the changes in optical parameters caused by implantation are proportional to the concentration of boron in GaN, the boron ion implantation applied to GaN-VCSELs causes optical absorption of 0.04% per round trip in the cavity and extends the light path of the cavity by 2.2 nm, both of which apparently have negligible impact on the operation of GaN-VCSELs. The implanted boron ions pass through the active regions, introducing non-radiative recombination centers at the edges of those active regions made of InGaN multi-quantum wells, which, however, does not cause significant current injection loss.

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By investigating the growth-rate dependence of GaInNAdGaAs MQ W grown by MOCVD, high-peflormance narrow-ridge laser diodes operating at 1 . 3~ have been demonstrated with a low threshold current of 25x4, a high characteristic temperature of 180K, and a long lifetime of I0,OOO hours under 1mW CW operation at room temperature.Recently, for optical-fiber telecommunication, 1.3pm GaInNAs lasers grown on GaAs substrates have attracted a great deal of attention. GaInNAs lasers have the advantage of a higher temperature insensitivity of the laser threshold and output, which could allow uncooled laser operation, compared to GaInAsP lasers. In addition GaInNAs lasers grown by MOCVD are relatively inexpensive to produce.We report here the growthrate dependence of GaInNAdGaAs multi-quantum wells (MQWs) grown by MOCVD and high-performance GaInNAs narrow -ridge laser diodes operating at 1 . 3~.The samples were grown by MOCVD on nGaAs (001) substrates tilted 10 degrees toward (110). The schematic device structure is shown in Fig. 1. Trimethylgallium, triethylindium, dimethylhydrazine and tertiarybutylarsine were the precursors used for Ga, In, N and As. The number of MQWs was varied from 2 to 4 . The growth temperature, the growth rate and the growth pressure were optimized at 490"C, 0.8pmhr-3.2pdhr and 150torr for the GaInNAs active layer, and 640"C, 5pmA-s and 150torr for the cladding layer. After the growth, the wafer was annealed for 2 minutes at 600°C in N. The GaJnNAs well-layer thickness was fixed at lOnm and the GaAs barrier-layer thickness was varied fiom 3nm to 17nm. The epitaxial wafer was processed into a 4pm-wide stripe index-guided structure by mesa etching and Si02 deposition. The wafer was then cleaved into a 400pm-length Fabry-Perot device with a reflectivity coating of 47% in front and 99% in the rear.The samples of GaInNAdGaAs DQW were grown at different growth rates under fixed GaInNAs composition, well thickness, barrier thickness, and growth temperature. Figure 2 shows the growth-rate dependence of the PL peak intensity at room temperature for these samples. The PL peak intensity was maximum at 1.5pm/hr. In addition, as a result of the optimization of the QW number and barrier thickness, minimum Ith was obtained at DQW laser with 7nm barrier thickness. The threshold current, slope efficiency and emission wavelength were 25mA, 0.24W/A and 1.297pm respectively. The LI-V characteristics are shown in Fig. 3. The temperature dependence of Ith is shown in Fig. 4. The characteristic temperature obtained between 10°C and 50°C was 180K. The estimated device lifetime under room temperature continuous-wave operation at 1mW is more than 10,000 hours.