GaN-based Blue-violet Laser Diodes Research Articles

Room-temperature continuous-wave operation of GaN-based blue-violet laser diodes with a lifetime longer than 1000 h

GaN-based continuous-wave operated blue-violet laser diodes (LDs) with long lifetime are demonstrated, which are grown on a c-plane GaN substrate by metal organic chemical vapor deposition with a 10 × 600 μm2 ridge waveguide structure. The electrical and optical characteristics of a blue-violet LD are investigated under direct-current injection at room temperature (25 °C). The stimulated emission wavelength and peak optical power of the LD are around 413 nm and over 600 mW, respectively. In addition, the threshold current density and voltage are as small as 1.46 kA/cm2 and 4.1 V, respectively. Moreover, the lifetime is longer than 1000 hours under room-temperature continuous-wave operation.

GaN基紫光激光器应用于激光引信抗干扰探索

GaN基紫光激光器应用于激光引信抗干扰探索

Publisher's Note: “Picosecond optical pulse generation from self-pulsating bisectional GaN-based blue-violet laser diodes” [Appl. Phys. Lett. 94, 161103 (2009)

Publisher's Note: “Picosecond optical pulse generation from self-pulsating bisectional GaN-based blue-violet laser diodes” [Appl. Phys. Lett. 94, 161103 (2009)

Picosecond optical pulse generation from self-pulsating bisectional GaN-based blue-violet laser diodes

Self-pulsations of 407 nm emitting GaN-based blue-violet laser diodes with bisectional (BS) electrodes were demonstrated by applying a reverse bias (VSA) to the subelectrode of the saturable absorber (SA) section. By increasing the injected current to the main electrode of the gain section with a reverse bias of VSA=−12 V, the optical pulses shortened to 30 ps. The optical peak output power was as high as 2.4 W with a pulse width of 30 ps and a repetition frequency of 0.9 GHz. This is so far the shortest pulse width from a self-pulsating BS GaN-based laser diode achieved by applying a reverse bias to the SA section.

Measurement of optical loss variation on thickness of InGaN optical confinement layers of blue-violet-emitting laser diodes

An optical loss of GaN-based blue-violet laser diodes (BV-LDs) was measured by taking the intensity decay of edge emitting luminescence with respect to the distance from cleaved edge of a wafer to the position where an excitation laser was focused. Amplified spontaneous emission (ASE) was also investigated by tuning the power of an excitation laser on BV-LD wafers. Measurements were performed on wafers with different thicknesses of InGaN optical confinement layers (OCLs). The threshold power of ASE intensity was minimized at an optimum thickness of InGaN OCL. We also found that optical loss of wafers was determined by absorption of an InGaN layer in thicker OCL structure. From experimental data and fittings, we obtained 40 cm−1 for InGaN absorption at 405 nm. The optical field confined in OCL region was reasonably high enough to affect the overall modal loss in devices. Therefore, the optical losses still remained even though the Mg-doped GaN regions are far enough from the active layers. The crystal quality of an InGaN layer should be an important aspect to improve the performance of BV-LDs.

Low current operation of GaN-based blue-violet laser diodes fabricated on sapphire substrate using high-temperature-grown single-crystal AlN buffer layer

Low current laser operation at 405 nm has been demonstrated for the first time for the devices fabricated on sapphire substrates by metalorganic chemical vapor deposition (MOCVD) using a high-temperature-grown single-crystal AlN buffer. The thick optical guiding layers were adopted to improve optical confinement. The device structure was the 2-μm-wide ridge-stripe type without facet coating. The minimum threshold current and current density were 60 mA and 3.8 kA/cm 2 for cavity lengths of 500 mm and 1 mm, respectively. These data were comparable to those reported using the special dislocation reduction techniques. The threshold current density linearly decreases with decreasing inverse of cavity length. It was expected that the low threshold current density ranging from 1 to 2 kA/cm 2 could be realized by adapting high reflection coating for laser facets. This expected current density was comparable to values realized for devices grown on the thick freestanding GaN as substrates. These findings support the promising potential of the HT-AlN buffer technique for production of advanced short-wavelength light-emitting devices on sapphire substrates.

High-power GaN-based blue-violet laser diodes with AlGaN∕GaN multiquantum barriers

AlGaN ∕ GaN multiquantum barriers (MQBs) were introduced into violet AlInGaN laser diodes with an InGaN multiquantum-well structure, resulting in drastic improvements in lasing performance. Comparing with conventional AlGaN single electron blocking layer (EBL), lower threshold current of 32mA and higher slope efficiency of 1.12W∕A at room temperature has been achieved by using the AlGaN∕GaN multiquantum barrier. This improvement implies that p-type AlGaN∕GaN MQBs are more effective in suppressing the overflow of electrons than p-type AlGaN single EBL. Effective barrier heights of the MQBs should be higher than the single EBL due to the quantum effect of MQBs and the enhancement of p-type doping efficiency. Additionally, the effect of strain on InGaN multiquantum wells from the single EBL can be reduced by using the AlGaN∕GaN MQBs structure.

Room-temperature operation of GaN-based blue-violet laser diodes fabricated on sapphire substrates using high-temperature-grown single-crystal AlN buffer layers

The laser operation has been demonstrated for the first time for the test devices fabricated on GaN layers grown on sapphire substrates by metalorganic chemical vapor deposition using high-temperature-grown single-crystal AlN buffer layers (HT-AlN buffer layers). The device structure was the simple electrode-stripe type with a 1-mm-long and 10-μm-wide laser cavity. The wavelength was 413 nm. The threshold current and current density were 760 mA and 7.6 kA/cm2, respectively. The operation voltage at the threshold current was 8 V. These characteristics were comparable to one of the best values reported using conventional low-temperature grown buffer layers, considering the used simple device structure. This fact was thought to support the promising potential of the HT-AlN buffer to realize high performance practical devices on sapphire substrates. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)