Threshold Current Of Laser Diodes Research Articles

Effect of Asymmetric InAlGaN/GaN Superlattice Barrier Structure on the Optoelectronic Performance of GaN-Based Green Laser Diode

An asymmetric InAlGaN/GaN superlattice barrier structure without the first quantum barrier layer (FQB) is designed, and its effect on the optoelectronic performance of GaN-based green laser diode (LD) has been investigated based on simulation experiment and analytical results. It is found that, compared with conventional GaN barrier LD, device performance is significantly improved by using FQB-free asymmetric InAlGaN/GaN superlattice barrier structure, including low threshold current, high output power, and high photoelectric conversion efficiency. The threshold current of LD with novel structure is 16.19 mA, which is 22.46% less than GaN barrier LD. Meanwhile, the output power is 110.69 mW at an injection current of 120 mA, which is 16.20% higher compared to conventional LD, and the wall-plug efficiency has an enhancement of 9.5%, reaching 20.27%. FQB-free asymmetric InAlGaN/GaN superlattice barrier layer can reduce optical loss, suppress the polarization effect, and improve the carrier injection efficiency, which is beneficial to improve output power and photoelectric conversion efficiency. The novel epitaxial structure provides theoretical guidance and data support for improving the optoelectronic performance of GaN-based green LD.

Study of the performance signature based ternary and quaternary III–V compounds for laser diodes in optical communication system

Abstract This study outlines the performance based ternary and quaternary III–V compounds in optical communication system. We have employed aluminum dopant ratio to check the effects in the spectral and thermal performance characteristics of various structures of optical diode sources based ternary and quaternary III–V compounds. The laser diode threshold current, reflection loss, corner wavelength, and optical gain are tested under various dopant aluminum ratios. The laser diode rise time and data flow rate are examined under thermal effects and various dopant levels. The laser diode corner wavelength and reflection loss can be enhanced by the increase of aluminum dopant ratio. The basic Al x In1−x Sb laser diode structure is the best candidate according to its high flow data rates in compared to other laser structures under the same thermal effects.

Realization of 366 nm GaN/AlGaN single quantum well ultraviolet laser diodes with a reduction of carrier loss in the waveguide layers

The performance of ultraviolet (UV) laser diodes (LDs) with a low Al mole fraction AlGaN cladding layer was investigated by varying the thicknesses of the waveguide layer. It is found that (1) the loss of carriers in the waveguide layer is much larger than that in blue or green LDs due to the shallower quantum well and consequently a weaker carrier confinement of UV lasers. (2) Carrier loss in the waveguide layer can be suppressed by using a thinner waveguide layer. Therefore, the threshold current of LDs can be reduced. (3) The ultraviolet GaN/AlGaN single quantum well laser diodes lasing at 366 nm are fabricated by using relatively thin AlGaN waveguide layers and low Al mole fraction AlGaN cladding layers.

The role of InGaN quantum barriers in improving the performance of GaN-based laser diodes

In this work, different aspects which have influences on device performance of blue laser diodes (LDs) when using InGaN instead of GaN as quantum barrier (QB) layers are investigated theoretically and experimentally. In the modeling calculation, it is found that the threshold current of LDs with InGaN QB layers is reduced obviously, but the slope efficiency is not largely improved due to the increase of leakage current. However, in the experimental results of the fabricated LDs using InGaN QB layers in comparison with those with GaN QB layers, the slope efficiency is really improved greatly, which is 34% higher. The great improvement of emission efficiency is ascribed to the better homogeneity of the active region which can improve the peak mode gain effectively. Such a better homogeneity of QW layers can be mainly attributed to the decreased composition pulling effect and a suppression of the stress between InGaN QB layers and InGaN QW layers.

Improvement of performance characteristics of deep violet InGaN DQW lasers using a strip DQW active region

The effect of the laser ridge width on the performance characteristics of deep violet In0.082Ga0.918N/GaN double quantum well (DQW) laser diodes (LDs) has been numerically investigated. Simulation results indicated that threshold current of LDs is decreased and slope efficiency and differential quantum efficiency (DQE) are increased by decreasing ridge width, whereas output power is decreased. The results also showed that a decrease of more than 1μm in the ridge width reduces the threshold current, whereas the slope efficiency, output power, and DQE are decreased. A new DQW LD structure with a strip active region has been proposed to obtain a lower current threshold and higher output power, slope efficiency, and DQE. The results showed the InGaN DQW LD with a strip DQW active region has the highest output power, slope efficiency, and DQE; it also has a lower threshold current compared with that of the original LD. The comparative study conducted for the LDs with output emission wavelengths of 390, 414 and 436nm has also confirmed the enhancement in LD performance using the strip DQW active region structure.

Low-threshold-current 1.2–1.5 μm laser diodes based on AlInGaAs/InP heterostructures

Separate confinement AlInGaAs/InP multiwell laser heterostructures emitting in a wavelength range of 1.2–1.5 μm have been synthesized by metalorganic vapor-phase epitaxy. The threshold current of laser diodes with a strip width of 4.5μm and a cavity length of 200μm was as low as 10 mA. With a cavity length of 1.0 mm, the threshold current density was 500–650 A/cm2. The laser diodes can operate in a continuous regime without forced cooling at an ambient temperature of up to 170°C. In a temperature range from 10 to 80°C, the characteristic temperature parameter T0 reached up to 110 K.

Laser diode facet modal reflectivity measurements

A simple and accurate method for measuring the front facet modal reflectivity of a Fabry-Perot laser diode is presented. In this method, optical feedback from an external mirror of known reflectivity, R(ext), is used to alter the laser diode threshold current. The effect of the external mirror and front facet reflectivities on the threshold current then allows for a measurement of the front facet modal reflectivity of the laser diode and is theoretically and experimentally studied. This method was used to measure a facet reflectivity of R(2) = 0.0151(+0.0018/-0.0032) [R(2) = 0.00592(+0.00085/-0.00123)] for a commercially antireflection-coated facet of a laser diode with a center wavelength of 795 nm (935 nm). The results of the reflectivity measurements based on the threshold current as a function of the external mirror reflectivity are compared with the results of the reflectivity measurements based on modulation depth of the optical spectrum [IEEE J. Quantum Electron. QE-19, 493 (1983)].

Temperature rise and thermal rise-time measurements of a semiconductor laser diode

A novel method is presented for measurement of the rise in temperature and thermal rise time of a semiconductor laser diode (LD) under pulsed operation. The technique employs the shift in LD threshold current which occurs with a rise in junction temperature. Practical results are given, showing a rise time of about 10 ns.

Effect of fixed emission wavelength on threshold current of InGaAsP semiconductor laser diodes

The authors demonstrate and quantify the extent to which a reduced variation of laser diode threshold current with temperature can be achieved by fixing lasing wavelength on the long wavelength side of the room temperature gain peak. This enhancement (To = 92K) occurs at the expense of increased threshold current at low temperatures. Fixing the lasing wavelength on the short wavelength side of the room temperature gain peak to reduce dynamic spectral broadening occurring at high modulation rates leads to reduced To (= 30K) in comparison to Fabry-Perot laser diodes To (= 42K) made from the same material.

Interface Recombination and Threshold Current in Grinsch-QW ALGaAs/GaAs Laser Diodes

ABSTRACTA series of Graded-Index Waveguide Separate-Confinement Heterostructure Quantum Well (GRINSCH-QW) laser diodes were grown by MBE at the systematically varied substrate temperatures. The threshold current of laser diodes were found to depend strongly on the growth temperature. The structure and electrical characteristics of the laser diodes were studied by double-crystal x-ray diffraction, I-V-T, C-V and deep level transient spectroscopy (DLTS). The interface recombination is found to be the dominant carrier transport process in the high threshold current laser diodes and is closely related to the presence of the high concentration of deep traps and interface states. In the low threshold current laser diodes, diffusion process is found to be the dominant carrier transport process.