Laser Physics and Laser Techniques (original) (raw)
Related papers
INTERFACE RECOMBINATION IN GaAs-GaAlAs QUANTUM WELLS
Le Journal de Physique Colloques, 1987
C e n t r e N a t i o n a l d ' E t u d e s d e s T t + l 6 c o m m u n i c a t i o n s , 196, Avenue H e n r i R a v e r a , F -9 2 2 2 0 B a g n e u x , F r a n c e R6sum6 : La duree de v i e non r a d i a t i v e dans des doubles h6terostructures GaAs;GaAlAs non dop6es fabriques en EJM e t EOM a Gt6 6tudiee en u t i l i s a n t une d t h o d e de d 6 c l i n de luminescence avec une r 6 s o l u t i o n de 10 ps. La v i t e s s e de recombinaison 2 l ' i n t e r f a c e S e s t obtenue en Ptudiant des s e r i e s d ' 6 c h a n t i l l o n s w a n t d i f f c r e n t e s Ppaisseurs d de GaAs ( e n t r e 1 P? e t 20 A). Pour chaque d r i e , S e s t constant quand d e s t superieur a 200 A. Quand d e s t i n f e r i e u r 2 200 A, S c r o i t du f a i t de l'augmentation de l a p r o b a b i l i t 6 de pr6sence des porteurs dans l a b a r r i i r e quand 1'6paisseur du p u i t s decroit. A b s t r a c t : Non r a d i a t i v e c a r r i e r s l i f e t i m e has been studied i n MBE and FR)CVD grown GaAs-GaA1 As undoped double heterostructures by luminescence decay technique. I n t e r f a c e recombination v e l o c i t y i s obtained by studying s e r i e s o f samples w i t h d i f f e r e n t GaAs l a y e r thicknesses d (between 1 , , m and 20 A). For each series S i s constant when d i s l a r g e r than 200 A. When d i s smaller than 200 A, S increases due t o the increase o f the l e a k i n g o f the c a r r i e r s wave functions i n the b a r r i e r when the w e l l thickness decreases.
Theory of reduced threshold current density in GaAs/AlGaAs quantum well lasers
Superlattices and Microstructures, 1990
It has recently been demonstrated that (111) GaAs/AlGaAs quantum well lasers can have a lower threshold current density than equivalent (001) lasers. We have used the envelope function method to calculate the hole confinement energies and valence subband dispersion energies of (111) and (001) quantum wells of varying width. We find that the differences in the vlrlence subband dispersion can account fully for the measured differences in threshold current densities. The heavy-hole mass is significantly larger dong (111) than aIong the conventional (001) growth direction. This increases the number of heavy-hole confined states for a given weJI width. Away from the zone centre, the subband dispersion in the well plane shows less mixing between heavy-and light-hole bands than for (001) growth and, in thin we&, the highest subband has a low in-plane effective mass over a greater energy range, resulting in a reduced density of states at the valence band maximum. Laser gain calculations show that this enhanced light-hole behaviour can explain the reduction in threshold current density of (111) lasers compared to equivalent (001) lasers, in good agreement with experimental observation. We also calculate optical matrix elements for TE and TM modes and find that in thin (111) lasers, an improved selection of TE over TM modes is possible, due mainly to the different subband orderings in the two growth directions. This leads to the elimination in (111) lasers of the TM jump of the laser mode observed in some (001) lasers and its replacement by a TE jump, in agreement with experimental observations.
IEEE Journal of Selected Topics in Quantum Electronics, 2002
By measuring the spontaneous emission (SE) from normally operating 1.3-m GaInNAs-GaAs-based lasers we have quantitatively determined the variation of each of the current paths present in the devices as a function of temperature from 130 K to 370 K. From the SE measurements we determine how the current close to threshold, varies as a function of carrier density n, which enables us to separate out the main current paths corresponding to monomolecular (defect-related), radiative or Auger recombination. We find that defect-related recombination forms 55% of the threshold current at room temperature (RT). At RT, radiative recombination accounts for 20% of th with the remaining 25% being due to nonradiative Auger recombination. Theoretical calculations of the threshold carrier density as a function of temperature were also performed using a ten-band
Recombination dynamics and lasing in ZnO∕ZnMgO single quantum well structures
Applied Physics Letters, 2007
We report a time-resolved study of the recombination dynamics in molecular beam epitaxy grown ZnO / ZnMgO single quantum wells ͑SQWs͒ of 1.0-4.5 nm width. The SQWs exhibit different emission properties, depending on both the well width and defect density. Stimulated emission has been achieved at room temperature in a separate confinement double heterostructure having a 3 nm wide SQW as an active region. It has been found that a critical parameter for the lasing is the inhomogeneous broadening of both QW and barrier emission bands.
Physical Review B, 1996
A quantum-mechanical calculation of radiative recombinations in cylindrical GaAs-͑Ga,Al͒As quantum-well wires excited by a cw laser in a photoluminescence experiment under quasistationary excitation conditions is performed. We work within the effective-mass approximation and the parabolic-band model for describing both electrons and holes, and consider, in the steady state, the interband absorption, and some radiative recombination mechanisms, such as recombination of electrons with free holes and with holes bound at acceptors. Carrier densities and electron-hole recombination decay times are calculated at room temperature and as functions of the laser intensity. For doped quantum-well wires, it is shown that the presence of acceptors substantially modifies the dependence on the laser intensity of the above quantities.
Optical gain in GaAsBi/GaAs quantum well diode lasers
Scientific Reports, 2016
Electrically pumped GaAsBi/GaAs quantum well lasers are a promising new class of near-infrared devices where, by use of the unusual band structure properties of GaAsBi alloys, it is possible to suppress the dominant energy-consuming Auger recombination and inter-valence band absorption loss mechanisms, which greatly impact upon the device performance. Suppression of these loss mechanisms promises to lead to highly efficient, uncooled operation of telecommunications lasers, making GaAsBi system a strong candidate for the development of next-generation semiconductor lasers. In this report we present the first experimentally measured optical gain, absorption and spontaneous emission spectra for GaAsBi-based quantum well laser structures. We determine internal optical losses of 10-15 cm −1 and a peak modal gain of 24 cm −1 , corresponding to a material gain of approximately 1500 cm −1 at a current density of 2 kA cm −2. To complement the experimental studies, a theoretical analysis of the spontaneous emission and optical gain spectra is presented, using a model based upon a 12-band k.p Hamiltonian for GaAsBi alloys. The results of our theoretical calculations are in excellent quantitative agreement with the experimental data, and together provide a powerful predictive capability for use in the design and optimisation of high efficiency lasers in the infrared. Recently, there has been a concerted effort to develop high-quality GaAs-based near-infrared diode lasers using the GaAsBi material system, and in particular to push their lasing wavelengths to the datacom/telecom wavelength range of 1.3-1.6 μ m. The main motivation behind this effort is due to the interesting properties of the GaAsBi alloy, which is formed by substituting relatively small quantities of bismuth in place of arsenic in GaAs 1. Incorporation of Bi in GaAs produces a strong reduction of the band gap, E g , (by up to ~80 meV per % Bi) due to valence band anti-crossing 1,2 , while also strongly increasing the spin-orbit-splitting energy, Δ SO 3,4 , between the top of the valence band and the spin-orbit-split-off band 4,5 , something which does not occur in conventional semiconductor alloys. The unusual impact of Bi incorporation on the (In)GaAs material properties opens up a range of possibilities for practical applications in semiconductor lasers 5 , photovoltaics 6 , spintronics 3 , photodiodes 7 and thermoelectrics 8. Highly appealing for the development of semiconductor lasers is the possibility to grow GaAsBi laser structures such that Δ SO > E g in the active region. This is highly significant as it promises to suppress the dominant efficiency-limiting loss processes in near-infrared lasers, namely Auger recombination, involving the generation of "hot" holes in the spin-orbit split-off band (the so-called "CHSH" process), and inter-valence band absorption (IVBA), where emitted photons are re-absorbed in the active region, thereby increasing the internal optical losses and negatively impacting upon the laser characteristics 9,10,11. This Δ SO > E g band structure is present in GaAsBi alloys containing > 10% Bi, at which composition the alloy band gap is close to 1.55 μ m on a GaAs substrate providing a promising route to devices such as efficient 1.55 μ m monolithic vertical cavity surface emitting lasers (VCSELs) 4,5. This, combined with the aforementioned ability to engineer the band structure to eliminate the dominant Auger and IVBA loss mechanisms, makes GaAsBi alloys an attractive candidate material system for the development of highly efficient, uncooled GaAs-based lasers for applications in optical communications 9. The first optically pumped GaAsBi based laser, consisting of a bulk-like 390 nm thick GaAs 0.975 Bi 0.025 active layer containing 2.5% Bi grown using molecular beam epitaxy (MBE) was reported by Tominaga et al. and achieved optically pumped pulsed operation up to a temperature of 240 K 12. This was followed by Ludewig et al. who demonstrated the first electrically pumped GaAsBi laser this time containing a quantum well (QW)-based
The Physics of the Quantum Well Laser
Physica Scripta, 1987
This paper reviews some of the properties of quantum well lasers (QWLs), with emphasis on the two-dimensional origins of these. It is shown that two main effects determine the lowering of threshold current, namely the diminished density of states (DOS) (favourable factor) and the diminished optical confinement (unfavorable factor). The good operation of GaAs-GaAlAs QWLs also relies on more subtle effects such as the square 2D DOS, the enhanced optical matrix element, the high quantum efficiency. .. The poor operation of GaInAs based quantum well lasers is due to the detrimental Auger effect which is larger than in 3D lasers because of the higher carrier densities at which QWLs operate. Several other useful properties of QWLs in the performance (high-frequency, narrow-line) and manufacturing fields are discussed. Problems and advantages of 1 and OD quantum-wire and quantum-box lasers are briefly evaluated.