A new semiconductor alloy material, GaAs1-xBix has been created by Metal Organic Vapor Phase Epitaxial (MOVPE) growth. A low growth temperature, such as 365°C, is required to obtain the alloy. X-ray diffraction measurements of alloy layers reveal that the diffraction patterns are satisfactory. The maximum GaBi content in the GaAsBi alloy estimated from the lattice constant is around 2%, which is consistent with that estimated from secondary ion mass spectroscopy (SIMS) measurements. In a photoluminescence (PL) measurement, a single peak spectrum is observed from 10 to 300 K. The temperature variation of the PL peak energy is as small as 0.1 meV/K.

New Semiconductor Alloy GaAs_ Bi_x Grown by Metal Organic Vapor Phase Epitaxy

Nanometre-scale semiconductor devices have been envisioned as next-generation technologies with high integration and functionality. Quantum dots, or the so-called ‘artificial atoms’, exhibit unique properties due to their quantum confinement in all 3D. These unique properties have brought to light the great potential of quantum dots in optoelectronic applications. Numerous efforts worldwide have been devoted to these promising nanomaterials for next-generation optoelectronic devices, such as lasers, photodetectors, amplifiers, and solar cells, with the emphasis on improving performance and functionality. Through the development in optoelectronic devices based on quantum dots over the last two decades, quantum dot devices with exceptional performance surpassing previous devices are evidenced. This review describes recent developments in quantum dot optoelectronic devices over the last few years. The paper will highlight the major progress made in 1.3 μm quantum dot lasers, quantum dot infrared photodetectors, and quantum dot solar cells.

https://iopscience.iop.org/article/10.1088/0022-3727/48/36/363001/pdf

Quantum dot optoelectronic devices: lasers, photodetectors and solar cells

Dynamic electromagnetic metamaterials

A theoretical and experimental study of the optical gain, refractive index change, and linewidth enhancement factor (LEF) of a p-doped quantum-dot (QD) laser is reported These parameters are measured by injecting an external pump, which induces cross-gain and cross-phase modulation A comprehensive theoretical model for the optical gain and refractive index change of InAs QD lasers is introduced with the quasi-equilibrium approximation of carrier distribution We use the Gaussian lineshape function for gain change and the confluent hypergeometric function of the first kind for refractive index change, which satisfies the Kramers-Kronig relation We match the experimental data with the theoretical results when the thermal effect is isolated by an additional pulsed current measurement We also calculate theoretically the optical gain, refractive index change, and LEF of an undoped QD laser of the same structure except the absence of p-type doping We show that the differential gain and LEF of the p-doped QD laser are improved compared with those of the undoped QD laser due to the reduced transparency carrier density

Theoretical and experimental study of optical gain, refractive index change, and linewidth enhancement factor of p-doped quantum-dot lasers

The combination of high-growth-temperature GaAs spacer layers and high-reflectivity (HR)-coated facets has been utilized to obtain low threshold currents and threshold current densities for 1.3-/spl mu/m multilayer InAs-GaAs quantum-dot lasers. A very low continuous-wave (CW) room-temperature threshold current of 1.5 mA and a threshold current density of 18.8 A/cm/sup 2/ are achieved for a three-layer device with a 1-mm HR/HR cavity. For a 2-mm cavity, the CW threshold current density is as low as 17 A/cm/sup 2/ for an HR/HR device. An output power as high as 100 mW is obtained for a device with HR/cleaved facets.

/pdf/high-performance-three-layer-1-3-spl-mu-m-inas-gaas-quantum-1zquye73ba.pdf

High-performance three-layer 1.3-/spl mu/m InAs-GaAs quantum-dot lasers with very low continuous-wave room-temperature threshold currents

We have measured modal gain and absorption data for doped and undoped quantum dot devices. We show that p doping results in an increase in the amount of gain available at a fixed current.

The effect of p - doping in In(Ga)As quantum dot lasers

An Indium Arsenide Bismide photodiode has been grown, fabricated, and characterized to evaluate its performance in the Mid Wave Infrared region of the spectrum. Spectral response from the diode has been obtained up to a diode temperature of 225 K. At this temperature, the diode has a cut off wavelength of 3.95 μm, compared to 3.41 μm in a reference Indium Arsenide diode, indicating that Bismuth has been incorporated to reduce the band gap of Indium Arsenide by 75 meV. Similar band gap reduction was deduced from the cut off wavelength comparison at 77 K. From the dark current data, shunt resistance values of 8 and 39 Ω at temperatures of 77 and 290 K, respectively, were obtained in our photodiode.

Demonstration of InAsBi photoresponse beyond 3.5 μm

The authors measure the temperature dependence of the components of threshold current of 1300?nm undoped and p-doped quantum dot lasers and show that the temperature dependence of the injection level necessary to achieve the required gain is the largest factor in producing the observed negative T0 in p-doped quantum dot lasers.

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Temperature dependence of threshold current in p-doped quantum dot lasers

We directly measure the gain and threshold characteristics of three quantum dot laser structures that are identical except for the level of modulation doping. The maximum modal gain increases at fixed quasi-Fermi level separation as the nominal number of acceptors increases from 0 to 15 to 50 per dot. These results are consistent with a simple model where the available electrons and holes are distributed over the dot, wetting layer, and quantum well states according to Fermi-Dirac statistics. The nonradiative recombination rate at fixed quasi-Fermi level separation is also higher for the p-doped samples leading to little increase in the gain that can be achieved at a fixed current density. However, we demonstrate that in other similar samples, where the difference in the measured nonradiative recombination is less pronounced, p doping can lead to a higher modal gain at a fixed current density.

/pdf/gain-in-p-doped-quantum-dot-lasers-3z3ys1hnkq.pdf

Gain in p-doped quantum dot lasers

The role of changes in gain and nonradiative recombination as a function of temperature in p-doped quantum dot samples that exhibit a minimum in the threshold current versus temperature characteristics are examined using a detailed analysis based on the multisection measurement method. An injection level is defined as the difference between the transparency energy and the transition energy of the dot states so that the results at different temperatures may be compared. The temperature dependence of the injection level necessary to achieve the required gain produces the initial decrease in nonradiative recombination current and threshold current between 250-280 K. At higher temperatures, the nonradiative recombination increases due to both an increase in the injection level required to achieve a fixed value of gain and because of an increase in the nonradiative recombination at fixed injection level. Using measurements of the population inversion function it is shown that the reduction in the injection level required to achieve a fixed value of gain between 250-280 K is caused by the thermalization of the carrier distribution over this temperature range. Subsequent increases in the injection level required to achieve a fixed value of gain are due to the increasing thermal distribution of carriers over the available states at higher temperatures.

Ian C. Sandall

Papers

The effect of p - doping in In(Ga)As quantum dot lasers

Demonstration of InAsBi photoresponse beyond 3.5 μm

Temperature dependence of threshold current in p-doped quantum dot lasers

Gain in p-doped quantum dot lasers

Temperature-Dependent Gain and Threshold in P-Doped Quantum Dot Lasers