Lateral carrier profile for mesa-structured InGaAs/GaAs lasers

Torre, M. S.; Esquivias, I.; Romero, B.; Czotscher, K.; Weisser, S.; Ralston, J.D.; Larkins, E. C.; Benz, W.; Rosenzweig, J.

doi:10.1063/1.364414

Cited by 4 publications

(6 citation statements)

References 16 publications

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“…That it is in good agreement with previously reported values 14 for strained InGaAs/ GaAs QW lasers, which where in the range of 1 -2 ϫ10 5 cm/s. Despite the relatively poor lateral carrier confinement, the estimated threshold carrier density of these oxide confined VCSELs is comparable to edge emitting lasers 2,11 and much lower than the estimated previously for implanted VCSELs. 3 This would indicate that carrier spreading due to diffusion is not seriously limiting the operation of the VCSELs studied in this work.…”

Section: ͑1͒mentioning

confidence: 89%

“…The radiative recombination coefficient estimated here, Bϳ1.3ϫ10 Ϫ10 cm 3 s Ϫ1 , is the same as the value recently reported in In 0.35 Ga 0.65 As/GaAs edge emitting multiple QW lasers. 11 The values of Auger recombination coefficients found in the literature present noticeable differences depending on the particular method of measurement and the material system. In general, the values reported for InGaAs QWs are higher than those for GaAs and AlGaAs QWs.…”

Section: ͑1͒mentioning

confidence: 99%

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Differential carrier lifetime in oxide-confined vertical cavity lasers obtained from electrical impedance measurements

Giudice¹,

Kuksenkov²,

Temkin³

et al. 1999

Applied Physics Letters

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Differential carrier lifetime measurements were performed on index-guided oxide-confined vertical cavity surface emitting lasers operating at 980 nm. Lifetimes were extracted from laser impedance measurements at subthreshold currents, with device size as a parameter, using a simple small-signal model. The carrier lifetimes ranged from 21 ns at 9 A, to about 1 ns at a bias close to threshold. For a 6ϫ6 m 2 oxide aperture device the threshold carrier density was n th ϳ2ϫ10 18 cm Ϫ3 . The effect of carrier diffusion was also considered. An ambipolar diffusion coefficient of D ϳ11 cm 2 s Ϫ1 was obtained. © 1999 American Institute of Physics. ͓S0003-6951͑99͒00507-0͔Carrier lifetime measurements are an important tool in semiconductor laser characterization. 1,2 Recently, a new electrical technique for differential carrier lifetime measurements was developed. 2 It originally applied to edge emitting lasers with bulk active region. More recently, it has been applied to vertical cavity surface emitting lasers ͑VCSELs͒ 3 with quantum wells ͑QWs͒ in the active region. In this letter, experimental results on differential carrier lifetimes in indexguided oxide-confined VCSELs are reported. Lifetimes were obtained from laser impedance measurements at subthreshold currents and the equivalent circuit modeling. Threshold carrier densities and the corresponding recombination parameters were calculated as a function of device size. In addition, the effect of lateral carrier diffusion out of the active region was also considered.Devices studied in this work were oxide-confined InGaAs VCSELs lasing at 980 nm. The current aperture was obtained by partial oxidation of two quarter-wavelength GaAlAs layers. 4 Lasers with aperture sizes in the range of 6-12 m had room temperature threshold currents from 220 to 600 A. The laser impedance was measured from 1 MHz up to 3 GHz. Measurements were performed for bias currents between 9 A and threshold. Figure 1 presents the frequency dependence of the measured impedance of a device with a ϳ8ϫ8 m 2 active region, with a threshold current I th Ϸ240 A, at 40 A of drive current. The measured laser impedance was modeled using the small-signal subthreshold equivalent circuit shown in the inset of Fig. 1. The parameters included in this model were the following: an inductance L associated with a bond wire, a parallel combination of a resistance R m and capacitance C m associated with the top mirror interfaces, and a parallel combination of a resistance R d and a capacitance C a representing the active region. The impedance of the bottom mirror was neglected. The total impedance of the circuit can be written aswhere d ϭR d C a is the characteristic time equal to the differential carrier lifetime. 5,6 This model does not consider the carrier transport and capture dynamics discussed elsewhere 7,8 because it was assumed that the capture time is small and the escape time from the wells is very large compared to the carrier lifetime in the wells. In this simple model, d is the effective lifetime of the carri...

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Section: ͑1͒mentioning

confidence: 89%

Section: ͑1͒mentioning

confidence: 99%

Differential carrier lifetime in oxide-confined vertical cavity lasers obtained from electrical impedance measurements

Giudice¹,

Kuksenkov²,

Temkin³

et al. 1999

Applied Physics Letters

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“…Under a positive bias, the graded hole injector facilitates the vertical hole transport from the Al 0.85 Ga 0. 15 As aperture region to the QDs by avoiding potential steps at heterointerfaces in the valence band and by providing a potential gradient directed toward the active layer.…”

Section: Sample Structure and Fabricationmentioning

confidence: 99%

“…14 However, the measurement of the diffusion length in a device structure under working conditions would be preferred for the understanding and optimization of device characteristics. This has been demonstrated in edge-emitting lasers by fitting the subthreshold electrical impedance and modulation response 15 or the threshold current dependence on the stripe width. 3 These methods rely on specific laser models and require additional assumptions (e.g., the shape of the gain-current curve).…”

Section: Introductionmentioning

confidence: 96%

Carrier diffusion in low-dimensional semiconductors: A comparison of quantum wells, disordered quantum wells, and quantum dots

et al. 2004

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International audienceWe present a comparative study of carrier diffusion in semiconductor heterostructures with different dimensionality [InGaAs quantum wells (QWs), InAs quantum dots (QDs), and disordered InGaNAs QWs (DQWs)]. In order to evaluate the diffusion length in the active region of device structures, we introduce a method based on the measurement of the current-voltage and light-current characteristics in light-emitting diodes where current is injected in an area <1 μm2. By analyzing the scaling behavior of devices with different sizes, we deduce the effective active area, and thus the diffusion length. A strong reduction in the diffusion length is observed going from QWs (Ld≈2.7 μm) to QDs (Ld<100 nm), DQWs being an intermediate case (Ldiff≈0–200 nm depending on the carrier density). These results show that lateral composition fluctuations, either intended or unintended, produce strong carrier localization and significantly affect the carrier profile in a device even at room temperatur

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“…Lateral carrier diffusion explains that the carrier lifetime obtained from experimental measurements of impedance below threshold is different from that obtained from measurement of spontaneous emission [15]. Rapid lateral carrier diffusion also leads to a strong damping of the relaxation oscillations, which can be observed in the small-signal modulation response [16,17], and which has important consequences in the dynamics.…”

Section: Introductionmentioning

confidence: 99%

Carrier dynamics in semiconductor lasers operating in the low-frequency fluctuation regime

Torre¹,

Masoller²,

Abraham³

et al. 2000

J. Opt. B: Quantum Semiclass. Opt.

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We analyse the dynamics of a weakly index-guided semiconductor laser operating near threshold and with optical feedback, using the Lang-Kobayashi model. Lateral effects are included, taking into account lateral carrier diffusion and a lateral profile for the optical field. The laser intensity fluctuates in a sequence of picosecond pulses, and the time-averaged intensity shows sudden dropouts to a nearly zero value, followed by gradual, steplike recoveries. We find that for large carrier diffusion the averaged intensity drops less frequently to zero and recovers less noisily than for low carrier diffusion. We analyse the time evolution of the carriers, and find that at the centre of the active region it fluctuates rapidly following the fast pulsing intensity. Further from the centre of the active region, diffusion has a preponderant effect and the carriers vary more smoothly in time (following the oscillations of the time-averaged intensity). Even further from the centre of the active region, the carrier profile is not influenced by the external optical feedback. The spatial variations of the carrier distribution and of the light intensity distribution within the mode seem to anticipate the occurrence of a dropout.

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Lateral carrier profile for mesa-structured InGaAs/GaAs lasers

Cited by 4 publications

References 16 publications

Differential carrier lifetime in oxide-confined vertical cavity lasers obtained from electrical impedance measurements

Differential carrier lifetime in oxide-confined vertical cavity lasers obtained from electrical impedance measurements

Carrier diffusion in low-dimensional semiconductors: A comparison of quantum wells, disordered quantum wells, and quantum dots

Carrier dynamics in semiconductor lasers operating in the low-frequency fluctuation regime

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