Quantum Well-dots Research Articles

Investigation of a p–i–n Photodetector with an Absorbing Medium Based on InGaAs/GaAs Quantum Well-Dots

Investigation of a p–i–n Photodetector with an Absorbing Medium Based on InGaAs/GaAs Quantum Well-Dots

Relationship between Wavelength and Gain in Lasers Based on Quantum Wells, Dots, and Well-Dots

Relationship between Wavelength and Gain in Lasers Based on Quantum Wells, Dots, and Well-Dots

Internal Loss in Diode Lasers with Quantum Well-Dots

Internal Loss in Diode Lasers with Quantum Well-Dots

Temperature Dependencies of Radiative and Nonradiative Carrier Lifetimes in InGaAs Quantum Well-Dots

Temperature Dependencies of Radiative and Nonradiative Carrier Lifetimes in InGaAs Quantum Well-Dots

Superluminescent Diodes Based on Chirped InGaAs/GaAs Quantum Well-Dot Layers

We study the applicability of InGaAs/GaAs quantum well-dots (QWDs) for active regions of broadband superluminescent diodes (SLDs) emitting in the 950–1150 nm spectral range; 2 mm long SLDs with a bent section and an active region based on seven chirped QWD layers show emission spectra centered at 1030 nm with a full-width at half-maximum of 80 nm and an output power of 2 mW. In a 250 µm long SLD with a tilted stripe that has an increased output loss, the width of the emission spectra is 113 nm at 20 °C and 120 nm at 60 °C.

Half-Ring Microlasers Based on InGaAs Quantum Well-Dots with High Material Gain

We report on half-ring lasers that are 100–200 µm in diameter and are fabricated by cleaving the initial full rings into halves. Characteristics of the half-ring and half-disk lasers fabricated from the same wafer are compared. The active area of the microlasers is based on the quantum heterostructures of mixed (0D/2D) dimensionality, referred to as quantum well-dots with very high material gain. Half-ring lasers show directional light emission and single-mode lasing near the threshold. A maximal continuous-wave output power of 76 mW is achieved for a half-ring that is 200 µm in diameter. Half-rings demonstrate better wall-plug efficiency as compared to half-disks. Lasing in pulse mode is observed up to 140 °C, the characteristic temperature is 100–125 K, depending on the half-ring size. P-side down bonding onto Si-board significantly improves power and temperature characteristics. In CW mode, lasing is maintained up to 97 °C, limited by active-area overheating.

Investigation of a p-i-n photodetector with an absorbing medium based on InGaAs/GaAs quantum well-dots

The static and dynamic characteristics of waveguide photodetectors with an absorbing region based on InGaAs/GaAs quantum well-dots were studied at room temperature. The absorption band of InGaAs/GaAs quantum well-dots is in the spectral range from 900 to 1100 nm. The waveguide photodetectors have a width of 50 μm and a length of the absorbing region from 92 μm to 400 μm. A low dark current density (1.1 and 22 μA/cm2 at -1 and -20 V) and cut off frequency of 5.6 GHz, limited by the time constant of a parasitic equivalent electric RC-circuit, were obtained. Keywords:waveguide photodetector, modulation frequency, quantum well-dots, integrated photonics.

Исследование p-i-n-фотодетектора с поглощающей средой на основе InGaAs/GaAs квантовых яма-точек

The static and dynamic characteristics of waveguide photodetectors with an absorbing region based on InGaAs/GaAs quantum well-dots were studied at room temperature. The absorption band of InGaAs/GaAs quantum well-dots is in the spectral range from 900 to 1100 nm. The waveguide photodetectors have a width of 50 µm and a length of the absorbing region from 92 µm to 400 µm. A low dark current density (1.1 и 22 μA/cm^2 at -1 и -20 V) and cut off frequency of 5.6 GHz, limited by the time constant of a parasitic equivalent electric RC circuit, were obtained.

Широкополосное излучение суперлюминесцентных диодов на основе многослойных структур с квантовыми яма-точками InGaAs/GaAs

We have studied superluminescent diodes with simplified design and active region based on 5 or 7 layers of InGaAs/GaAs quantum well-dots (QWDs). Emission peaks of the individual QWD layers are shifted with respect to each other by 15-35 nm to provide as wide as possible emission line in a superluminescent mode with central wavelength of about 1 µm without significant spectral dips. For superluminescent diodes with the active region based on 5 and 7 QWD layers, the maximal value of full width at half maximum of emission spectrum was 92 and 103 nm respectively.

Model for speed performance of quantum-dot waveguide photodiode

A model is proposed that makes it possible to analytically analyze the speed performance of a waveguide p-i-n photodiode with a light-absorbing region representing a multilayered array of quantum dots separated by undoped spacers. It is shown that there is an optimal number of layers of quantum dots, as well as an optimal thickness of the spacers, which provide the widest bandwidth. The possibility of achieving a frequency range (at the level of -3 dB) above 20 GHz for waveguide photodiodes based on InGaAs/GaAs quantum well-dots is shown Keywords: photodiode, quantum dots, speed.

Модель быстродействия волноводного фотодиода с квантовыми точками

A model is proposed that makes it possible to analytically analyze the speed performance of a waveguide p-i-n photodiode with a light-absorbing region representing a multilayered array of quantum dots separated by undoped spacers. It is shown that there is an optimal number of layers of quantum dots, as well as an optimal thickness of the spacers, which provide the widest bandwidth. The possibility of achieving a frequency range (at the level of -3 dB) above 20 GHz for waveguide photodiodes based on InGaAs/GaAs quantum well-dots is shown.

Time-resolved temperature-dependent photoluminescence spectroscopy of InGaAs/GaAs quantum well-dots

The paper presents the results of a study of dynamic properties of InGaAs quantum well-dots (QWD) embedded in a GaAs matrix carried out by time-resolved photoluminescence (TRPL) in the temperature range of 10–300 K. The time dependence of the PL shows a long region of constant signal intensity. It was attributed to the filling of all available QWD states due to the fast exchange with the matrix and the relatively long time of radiative recombination. The experimental results are consistent with the calculations performed in the rate equation model for a two-level system. It turned out that there is no need for the residual 2D quantum well to be taken into account, which is not typical for Stranski-Krastanow quantum dots, where the wetting layer plays an important role in carrier exchange processes. Nonradiative recombination can also be ignored, which indicates a high quality of the structure. By fitting the simulation results, the microscopic properties of the electron and hole states in QWDs were obtained for the first time: the radiative lifetime is 700 ps, the barriers for electron and hole in QWDs are 50 and 150 meV, respectively. Carrier capture time was found to be in the range of 10–30 ps.

Half-disk lasers with active region based on InGaAs/GaAs quantum well-dots

Half-disk lasers fabricated by cleaving initial full-disk lasers have an advantage of directional light outcoupling as well as increased output power and efficiency as compared to full-disk lasers of the same diameter. The continuous wave output power of a 200 µm diameter half-disk laser exceeds 70 mW. Quasi single-mode lasing with a high side-mode suppression ratio more than 20 dB is demonstrated for half-disk lasers of various diameters. A maximum 3 dB small signal modulation frequency of 4.9 GHz was measured for a 100 µm in diameter half-disk laser.

Relationship between wavelength and gain in lasers based on quantum wells, dots, and well-dots

A systematic study of a series of InGaAs/GaAs lasers in the 1-1.3 μm optical range based on quantum wells (2D), quantum dots (0D), and quantum well-dots of transitional (0D/2D) dimensionality is presented. In a wide range of pump currents, the dependences of the lasing wavelength on the layer gain constant, a parameter which allows comparing lasers with different types of active region and various waveguide designs, are measured and analyzed. It is shown that the maximum optical gain of the quantum well-dots is significantly higher, and the range of lasing rawavelengths achievable in edge-emitting lasers without external resonators is wider than in lasers based on quantum wells and quantum dots. Keywords: semiconductor laser, quantum well, quantum dots, quantum well-dots, optical gain.

Internal loss in diode lasers with quantum well-dots

The internal loss at the lasing threshold were studied experimentally and numerically in laser cavities comprising dense arrays of InGaAs/GaAs quantum dots (quantum well-dots) as a function of the number of their planes and the output loss. Numerical values of the parameters were found that determine the free-carrier absorption in the active region and in the waveguiding layer. The optimal design of the laser diode was determined to achieve the highest external differential efficiency. Keywords: diode lasers, semiconductor nanostructures, internal loss.

Бимодальность в спектрах электролюминесценции InGaAs квантовых яма-точек

The electroluminescence spectra of waveguiding structures based on quantum well-dots were investigated with polarization resolution in the temperature range of 60−300 K. It is found that the ground state emission consists of two peaks with different degrees of TE-polarization and these peaks are getting closer with temperature decrease. We attribute the bimodality to the existence of two different types of nanoobjects in the active region: the quantum well-dots, which have partially TE-polarized emission, and quantum dots emitting almost fully TE-polarized light.

Temperature dependencies of radiative and nonradiative carrier lifetimes in InGaAs quantum well-dots

Heterostructure with InGaAs/GaAs quantum well-dots was investigated in temperature range 10-300 K using photoluminescence spectroscopy in CW mode as well with time resolution. Obtained decay times were splitted into radiative and nonradiative components of carrier lifetime. It is found that radiative lifetime demonstrates exponential growth with temperature rise, while temperature dependence of nonradiative one is much weaker. Keywords: semiconductors, quantum well-dots, photoluminescence, time resolution, lifetime, temperature dependence.

Bimodality in the electroluminescence spectra of quantum well-dots InGaAs nanostructures

The electroluminescence spectra of waveguiding structures based on quantum well-dots were investigated with polarization resolution in the temperature range of 60-300 K. It is found that the ground state emission consists of two peaks with different degrees of TE-polarization and these peaks are getting closer with temperature decrease. We attribute the bimodality to the existence of two different types of nanoobjects in the active region: the quantum well-dots, which have partially TE-polarized emission, and quantum dots emitting almost fully TE-polarized light. Keywords: Electroluminescence, quantum dots, InGaAs heterostructures, waveguide structures, emission polarization.

Быстродействующие фотодетекторы на основе квантовых ям-точек InGaAs/GaAs

High-speed photodetectors (PDs) based on InGaAs/GaAs quantum well-dots (QWDs) nanostructures are investigated. The -3 dB bandwidth of 8.2 GHz at 905 nm has been demonstrated. It is shown that internal processes in QWDs make it possible to create a PD with a bandwidth of up to 12.5 GHz, and the processes of thermalization of carriers from QWD layers do not limit the speed at reverse biases of more than 5 V.

Температурные зависимости излучательного и безызлучательного времени жизни носителей в квантовых яма-точках InGaAs

Heterostructure with InGaAs/GaAs quantum well-dots was investigated in temperature range 10-300 K using photoluminescence spectroscopy in CW mode as well with time resolution. Obtained decay times were splitted into radiative and nonradiative components of carrier lifetime. It is found that radiative lifetime demonstrates exponential growth with temperature rise, while temperature dependence of nonradiative one is much weaker.