Progress in long-wavelength strained-layer InGaAs(P) quantum-well semiconductor lasers and amplifiers

The band gap dependencies of the threshold current and its radiative component are measured using high pressure techniques. Detailed theoretical calculations show that the band gap dependence of the internal losses plays a significant role in the band gap dependence of the radiative current. Temperature dependence measurements show that the radiative current accounts for 20% of the total threshold current at room temperature. This allows us to determine the pressure dependence of the non-radiative Auger recombination current, and hence to experimentally obtain the variation of the Auger coefficient C with band gap. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2722041͔The relative importance of different carrier recombination processes occurring in semiconductor diode lasers is strongly dependent on the band structure, material quality and laser geometry ͑e.g., cavity length, facet coatings, etc.͒. While a small amount of radiative recombination via spontaneous emission is desirable ͑to seed the stimulated emission process͒, other nonradiative recombination paths may contribute to the laser threshold current and are detrimental to the performance of the devices. For InGaAs͑P͒ / InP devices operating over the telecommunications range ͑1.3-1.6 m͒, it is known that Auger recombination plays an important role and is responsible for their high temperature sensitivity [1][2][3][4] . In order to understand these limiting processes and consequently to improve the performance of the devices, it is necessary to separate the contribution of the different recombination current paths. 1-6 Hydrostatic pressure is an ideal tool to investigate the current paths and their variation with band gap, and hence operating wavelength. In long wavelength semiconductor multiple quantum well lasers where leakage currents are small, it has been shown 1,5 that the threshold current I th can be written as the sum of monomolecular ͑ϰn͒, radiative ͑ϰn 2 ͒, and Auger ͑ϰn 3 ͒ recombination currents, where n is the carrier density at threshold ͑assuming that the hole and electron densities are equal͒. Thus I th = eV͑An + Bn 2 + Cn 3 ͒ where e is the electronic charge, V is the volume of the active region, and A, B, and C are the monomolecular, radiative, and Auger recombination coefficients, respectively. Good growth quality means that the monomolecular current is negligible in the InGaAs devices studied here. 1,5 The relative magnitudes of the remaining radiative and nonradiative currents have been experimentally studied via temperature and high pressure measurements. 1,5 Previous analyses were based on the theoretical assumption that for an ideal quantum well laser, the radiative current is proportional to the square of the band gap: I rad ϰ E g 2 , where E g is the band gap 7 although this had not been experimentally verified at room temperature. The pressure dependence of the radiative current has already been verified at low temperatures using a helium gas pressure system. 8 Since at cryogenic temperatures ͑T Ͻ 120 K͒ all of the inje...

mentioning

confidence: 99%

mentioning

confidence: 99%

Experimental determination of the band gap dependence of Auger recombination in InGaAs∕InP multiple quantum well lasers at room temperature

Massé

Adams

Sweeney

2007

“…5 However, little is known about the properties of compressively strained quantum-well lasers in this wavelength region. The advantages of using compressively strained active layers, for both InGaAs and InGaAsP quantum-well lasers with emission at 980 nm, 6 1.3 m, 7 and 1.55 m, 8 has been well established. Similar improvements in performance ͑i.e., lower transparency current and higher differential gain͒ can be expected from incorporating compressive strain into InGaAsP quantum wells for laser emission in the 730-780 nm range.…”

mentioning

confidence: 99%

730-nm-emitting Al-free active-region diode lasers with compressively strained InGaAsP quantum wells

Al-Muhanna

Wade

Mawst

et al. 1998

0.73-m-emitting, Al-free active-region, strained (⌬a/aϷ1.4%) InGaAsP single-quantum-well diode lasers have been grown by low-pressure metal-organic chemical-vapor deposition. A broad waveguide laser design with In 0.5 ͑Ga 0.5 Al 0.5 ͒ 0.5 P cladding layers is utilized to achieve a large effective transverse spot size (d/⌫ϭ0.433 m) and to minimize carrier leakage from the active region. Threshold current densities of 514 A/cm 2 ͑100-m-wide stripe, Lϭ1 mm͒, external differential quantum efficiencies of 60%, and characteristic temperature coefficients for the threshold current, T 0 , and external differential quantum efficiency characteristic temperature, T 1 , have values of 72 and 153 K, respectively. Continuous wave output powers of 1.4 W are obtained from facet-coated (90%/10%) devices operating at 735 nm. © 1998 American Institute of Physics. ͓S0003-6951͑98͒01306-0͔High output power diode lasers with wavelengths in the 730-780 nm range are needed for a variety of applications ranging from laser printing and optical recording to cancer treatments such as photodynamic therapy. For wavelengths less than 840 nm, typical laser structures use AlGaAs in the active region, which can result in long-term reliability problems. As the emission wavelength decreases less than 780 nm, the high aluminum content of the Al x Ga 1Ϫx As active layer (xϾ0.1) makes reliable high-power operation increasingly difficult to achieve. Using a specially processed oxygen gettered aluminum source for the metal-organic chemicalvapor deposition ͑MOCVD͒ growth process, AlGaAs activelayer devices ͑100-m-wide emission aperture͒ have been reported with continuous wave ͑cw͒ output powers of 540 mW at an emission wavelength of 715 nm. 1 More recently, compressively strained AlGaInAs active-layer lasers have been reported in the 730-nm wavelength range demonstrating 2.2-W cw output powers from broad-stripe ͑100-mwide͒ devices. 2 Although high output powers have been obtained from the AlGa͑In͒As active-layer devices, 1,2 longterm reliability is still an open question.The use of an InGaAsP active-region offers an attractive alternative to conventional AlGaAs-based structures for short-wavelength, high-power sources. The lower surface recombination velocity of InGaAsP compared with AlGaAs leads to a dramatic reduction in facet-temperature rise during high-power cw operation. 3 In fact, Al-free active-region lasers in the 800-nm-wavelength region have recently demonstrated catastrophic optical mirror damage ͑COMD͒ at an internal power density, P COMD , of 17.5 MW/cm 2 , which is more than twice the value reported for AlGaAs active devices at the same wavelength. 4 Another advantage of using an InGaAsP-based active region is the ability to employ a strained-layer or strain-compensated quantum-well active region. Tensile-strained ͑In͒ GaAsP active-layer lasers have been reported operating in the 700-800 nm wavelength range. 5 However, little is known about the properties of compressively strained quantum-well lasers in this wavelength region. The advantag...

“…Our low-temperature, high-pressure data confirm the results of previous atmospheric pressure measurements on the same devices which indicated a transition in the dominant recombination mechanism from radiative to Auger as the device temperature is increased from ϳ100 to 300 K. Much work has been focused on the fundamental optical processes and the limiting factors in these laser systems. [1][2][3][4][5][6][7][8][9][10][11][12] Such knowledge enables us to investigate the scope for further device optimization by means of band structure engineering in low-dimensional heterostructure systems such as quantum-wells (QWs), quantum barriers, quantum wires, and quantum dots. In general, the threshold current, I th , of semiconductor lasers may be considered to consist of four carrier density, n, dependent recombination channels, 13,14 namely, monomolecular recombination ͑ϰn͒ which describes recombination via traps and defects, band-to-band radiative recombination ͑ϰn 2 ͒, Auger recombination ͑ϰn 3 ͒, and carrier leakage.…”

mentioning

confidence: 99%

“…The detailed growth procedures of these devices can be found elsewhere. 10 All of the lasers were as-cleaved with a cavity length of 500 m and were investigated in unmounted chip form. The optical pressure cell, mounted inside a liquid nitrogen bath cryostat was used in conjunction with Unipress U11 helium gas compressor capable of generating pressures up to 15 kbar.…”

mentioning

confidence: 99%

Radiative and Auger recombination in 1.3μm InGaAsP and 1.5μm InGaAs quantum-well lasers measured under high pressure at low and room temperatures

Jin

Sweeney

Ahmad

et al. 2004

Single-mode quantum cascade lasers employing asymmetric Mach-Zehnder interferometer type cavities Appl. Phys. Lett. 101, 161115 (2012) Bistability patterns and nonlinear switching with very high contrast ratio in a 1550nm quantum dash semiconductor laser Appl. Phys. Lett. 101, 161117 (2012) Relative intensity noise of a quantum well transistor laser Appl. Phys. Lett. 101, 151118 (2012) Blue monolithic AlInN-based vertical cavity surface emitting laser diode on free-standing GaN substrate Appl. Phys. Lett. 101, 151113 (2012) Ground state terahertz quantum cascade lasers