Browsing by Author "Sun, CK"

Now showing 1 - 4 of 4

Carrier-carrier scattering in GaAs/AlxGa1-xAs quantum wells
(2000-06-15)
Sun, KW
;
Song, TS
;
Sun, CK
;
Wang, JC
;
Kane, MG
We have studied carrier dynamics in highly nonequilibrium two-dimensional (2D) carrier distributions generated with femtosecond laser pulses in p-doped GaAs/Al0.32Ga0.68As quantum wells at photoexcited carrier densities between 10(9) and 10(11) cm(-2). The initially nonthermal carrier distribution is quickly broadened due to inelastic carrier-carrier scattering, with the broadening rate increasing as carrier density is increased. Measurements of the unrelaxed peak height in the hot electron-neutral acceptor luminescence spectra are compared with calculations of the carrier distribution using integration of the 2D dynamically screened Boltzmann equation. Our results indicate that carrier-carrier scattering becomes as significant a scattering mechanism as LO-phonon emission at density of about 10(10) cm(-2).
Carrier-carrier scattering: an experimental comparison of 5 and 3 nm AlxGa1-xAs/GaAs quantum wells
(2000)
Sun, KW
;
Sun, CK
;
Wang, JC
;
Wang, SY
;
Lee, CP
We have studied carrier dynamics among highly nonequilibrium carrier distributions generated with femtosecond laser pulses in Be:AlxGa1-xAs/GaAs quantum wells with different well width at hot carrier densities between 10(9) and 10(11) cm(-2). The spectra, at moderately high densities (greater than or equal to 10(10) cm(-2)) indicate that the initially narrow electron distribution is altered in a time less than or equal to the LO-phonon emission time, as a result of rapid carrier-carrier scattering. At an excitation density of about 10(10) cm(-2), the carrier-carrier scattering rate is faster in narrower quantum wells. By measuring the intensity of the unrelaxed peak, it is possible to determine the relative rates of carrier-carrier scattering and LO-phonon emission. Our results indicate that carrier-carrier scattering becomes as significant as LO-phonon emission at a density of about 1 x 10(10) cm(-2) in the 5 nm quantum wells. (C) 2000 Elsevier Science Ltd. All rights reserved.
Separated-transport-recombination p-i-n photodiode for high-speed and high-power performance
(2005-08-01)
Shi, JW
;
Hsu, HC
;
Huang, FH
;
Liu, WS
;
Chyi, JI
We demonstrate a novel p-i-n photodiode (PD) structure, the separated-transport-recombination PD, which can greatly relieve the tradeoffs among the resistance-capacitance bandwidth limitation, responsivity, and output saturation power performance. Incorporating a short carrier lifetime (less than 1 ps) epitaxial layer to serve as a recombination center, this device exhibits superior speed and power performance to a control PD that has a pure intrinsic photoabsorption layer. Our demonstrated structure can also eliminate the bandwidth degradation problem of the high-speed photodetector, whose active photoabsorption layer is fully composed of short lifetime (similar to 1 ps) materials, under high dc bias voltages.
Ultrafast carrier-carrier scattering in AlxGa1-xAs/GaAs quantum wells
(1999-12-01)
Sun, KW
;
Song, TS
;
Sun, CK
;
Wang, JC
;
Wang, SY
We present new time-resolved measurements that demonstrate the effect of injected carrier densities on carrier-carrier scattering rates of a highly nonequilibrium carrier distribution in the p-doped Al0.32Ga0.68As/GaAs quantum wells. The initially photoexcited nonthermal carrier distribution is quickly broadened due to rapid increase of the inelastic carrier-carrier scattering as the injected carrier densities increased toward 10(11) cm(-2). (C) 1999 Elsevier Science B.V. All rights reserved.