01436nas a2200241 4500008004500000020001400045245009100059210006900150260000800219300001200227490000700239520073900246653001800985653001201003100001801015700001401033700002001047700001801067700002001085700002001105700002001125856004901145 1996 Engldsh a0003-695100aTemperature of quasi-two-dimensional electron gases under steady-state terahertz drive0 aTemperature of quasitwodimensional electron gases under steadyst cFeb a829-8310 v683 a
We use photoluminescence to study the time-average energy distribution of electrons in the presence of strong steady-state drive at terahertz (THz) frequencies, in a modulation-doped 125 Angstrom AlGaAs/GaAs square well that is held at low lattice temperature TL. We find that the energy distribution can be characterized by an effective electron temperature, T-e(>T-L), that agrees well with values estimated from the THz-illuminated, dc conductivity. This agreement indicates that under strong THz drive, LO phonon scattering dominates both energy and momentum relaxation; that the carrier distribution maintains a heated, thermal form; and that phonon drift effects are negligible. (C) 1996 American Institute of Physics.
10ahot-electrons10aPhysics1 aAsmar, N., G.1 aCerne, J.1 aMarkelz, A., G.1 aGwinn, E., G.1 aSherwin, M., S.1 aCampman, K., L.1 aGossard, A., C. uhttps://markelz.physics.buffalo.edu/node/25801295nas a2200241 4500008004100000020001400041245007000055210006900125260001100194300001400205490000700219520060900226100001400835700001900849700001900868700002000887700002100907700002000928700001600948700002000964700002000984856004901004 1996 eng d a0031-900700aUndressing a collective intersubband excitation in a quantum well0 aUndressing a collective intersubband excitation in a quantum wel cMar 25 a2382-23850 v763 aWe have experimentally measured the 1-2 intersubband absorption in a single 40 nm wide modulation-doped Al0.3Ga0.7As/GaAs square quantum well as a function of frequency, intensity, and charge density. The low-intensity depolarization-shifted absorption occurs near 80 cm(-1) (10 meV or 2.4 THz), nearly 30% higher than the intersubband spacing. At higher intensities, the absorption peak shifts to lower frequencies. Our data are in good agreement with a theory proposed by Zaluzny, which attributes the redshift to a reduction in the depolarization shift as the excited subband becomes populated.
1 aCraig, K.1 aGaldrikian, B.1 aHeyman, J., N.1 aMarkelz, A., G.1 aWilliams, J., B.1 aSherwin, M., S.1 aCampman, K.1 aHopkins, P., F.1 aGossard, A., C. uhttps://markelz.physics.buffalo.edu/node/26501583nas a2200241 4500008004100000020001400041245006200055210006100117260001100178300001200189490000700201520093300208100002001141700001401161700001901175700001501194700001601209700001601225700001501241700002001256700001601276856004901292 1995 eng d a0167-278900aNONLINEAR QUANTUM DYNAMICS IN SEMICONDUCTOR QUANTUM-WELLS0 aNONLINEAR QUANTUM DYNAMICS IN SEMICONDUCTOR QUANTUMWELLS cMay 15 a229-2420 v833 aWe discuss recent measurements of the nonlinear response of electrons in wide quantum wells driven by intense electromagnetic radiation at terahertz frequencies. The theme is the interplay of quantum mechanics, strong periodic driving, the electron-electron interaction and dissipation. We discuss harmonic generation from an asymmetric double quantum well in which the effects of dynamic screening are important. Measurements and theory are found to be in good agreement. We also discuss intensity-dependent absorption in a 400 Angstrom square quantum well. A new nonlinear quantum effect occurs, in which the frequency at which electromagnetic radiation is absorbed shifts to the red with increasing intensity. The preliminary experimental results are in agreement with a theory by Zaluzny, in which the source of the nonlinearity is the self-consistent potential in the Hartree approximation for the electron dynamics.
1 aSherwin, M., S.1 aCraig, K.1 aGaldrikian, B.1 aHeyman, J.1 aMarkelz, A.1 aCampman, K.1 aFafard, S.1 aHopkins, P., F.1 aGossard, A. uhttps://markelz.physics.buffalo.edu/node/27200682nas a2200217 4500008004100000020001400041245011500055210006900170260001100239300001400250490000700264100001400271700002000285700002000305700001800325700001700343700002000360700001900380700001600399856004900415 1995 eng d a0163-182900aQUENCHING OF EXCITONIC QUANTUM-WELL PHOTOLUMINESCENCE BY INTENSE FAR-INFRARED RADIATION - FREE-CARRIER HEATING0 aQUENCHING OF EXCITONIC QUANTUMWELL PHOTOLUMINESCENCE BY INTENSE cFeb 15 a5253-52620 v511 aCerne, J.1 aMarkelz, A., G.1 aSherwin, M., S.1 aAllen, S., J.1 aSundaram, M.1 aGossard, A., C.1 aVanson, P., C.1 aBimberg, D. uhttps://markelz.physics.buffalo.edu/node/26200655nas a2200217 4500008004100000020001400041245008000055210006900135260001100204300001600215490000700231100001800238700002000256700001800276700001400294700002000308700002000328700002000348700002000368856004900388 1995 eng d a0163-182900aRESONANT-ENERGY RELAXATION OF TERAHERTZ-DRIVEN 2-DIMENSIONAL ELECTRON GASES0 aRESONANTENERGY RELAXATION OF TERAHERTZDRIVEN 2DIMENSIONAL ELECTR cJun 15 a18041-180440 v511 aAsmar, N., G.1 aMarkelz, A., G.1 aGwinn, E., G.1 aCerne, J.1 aSherwin, M., S.1 aCampman, K., L.1 aHopkins, P., F.1 aGossard, A., C. uhttps://markelz.physics.buffalo.edu/node/25900527nas a2200169 4500008004100000245007300041210006900114300001000183490000900193100001800202700001800220700002000238700001900258700001500277700001600292856004900308 1994 eng d00aFar-infrared harmonic generation from semiconductor heterostructures0 aFarinfrared harmonic generation from semiconductor heterostructu a48-550 v18541 aMarkelz, A.G.1 aGwinn, E., G.1 aSherwin, M., S.1 aHeyman, J., N.1 aNguyen, C.1 aKroemer, H. uhttps://markelz.physics.buffalo.edu/node/31901316nas a2200229 4500008004100000020001400041245006500055210006300120260000800183300001200191490000600203520067700209100001400886700001800900700001900918700002000937700002000957700002000977700002000997700002001017856004901037 1994 eng d a0268-124200aFAR-INFRARED SATURATION SPECTROSCOPY OF A SINGLE SQUARE-WELL0 aFARINFRARED SATURATION SPECTROSCOPY OF A SINGLE SQUAREWELL cMay a627-6290 v93 aWe have performed saturation spectroscopy measurements of the lowest intersubband transition in a single 400 angstrom GaAs/Al0.3Ga0.7As modulation-doped square quantum well. We couple intense tunable far-infrared radiation from the Santa Barbara free electron laser into our sample using an edge-coupling technique and measure absorption as a function of frequency and intensity. Saturation and frequency shifts in the absorption line are clearly observed. We attribute the frequency shifts to reductions in the many-body depolarization shift. From our preliminary measurements, we estimate the intersubband relaxation time to be 600 ps to within a factor of three.
1 aCraig, K.1 aFelix, C., L.1 aHeyman, J., N.1 aMarkelz, A., G.1 aSherwin, M., S.1 aCampman, K., L.1 aHopkins, P., F.1 aGossard, A., C. uhttps://markelz.physics.buffalo.edu/node/26401624nas a2200193 4500008004100000020001400041245011200055210006900167260001200236300001400248490000700262520102300269100002001292700001801312700002001330700001501350700001601365856004901381 1994 eng d a0038-110100aGIANT 3RD-ORDER NONLINEAR SUSCEPTIBILITIES FOR INPLANE FAR-INFRARED EXCITATION OF SINGLE INAS QUANTUM-WELLS0 aGIANT 3RDORDER NONLINEAR SUSCEPTIBILITIES FOR INPLANE FARINFRARE cApr-Jun a1243-12450 v373 aThird-order, free-carrier nonlinear susceptibilities, chi(3), have been measured between 19 and 23 cm-1 for three InAs/AlSb quantum wells with sheet densities between 2.5 x 10(12) cm-2 and 8 x 10(12) cm-2. We find that these wells are strongly nonlinear at far-infrared frequencies: odd harmonics ninth order have been observed at high incident intensities, and the peak value of chi(3) reaches approximately 1 esu. This is several orders of magnitude larger than previously reported values for chi(3) in bulk n-GaAs (10(-4) esu)[1] and in polyacetylene (10(-7) esu)[2]. The large magnitude of chi(3) is attributed to the high carrier density in the InAs wells, and to the strong non-parabolicity of the conduction band in InAs. However, the free-carrier chi(3) for bulk InAs predicts a density-dependence different from that observed, and the measured decrease in chi(3) with increasing intensity indicates non-perturbative response. We find that the anisotropy of chi(3) displays the expected 4-fold symmetry.
1 aMarkelz, A., G.1 aGwinn, E., G.1 aSherwin, M., S.1 aNguyen, C.1 aKroemer, H. uhttps://markelz.physics.buffalo.edu/node/26901594nas a2200337 4500008004100000020001400041245009400055210006900149260000800218300001200226490000900238520066100247100001800908700001400926700001800940700001800958700001900976700002100995700001701016700002001033700001501053700001801068700002001086700002001106700002001126700002001146700001301166700001201179700001601191856004901207 1994 eng d a0022-231300aPROBING TERAHERTZ DYNAMICS IN SEMICONDUCTOR NANOSTRUCTURES WITH UCSB FREE-ELECTRON LASERS0 aPROBING TERAHERTZ DYNAMICS IN SEMICONDUCTOR NANOSTRUCTURES WITH cApr a250-2550 v60-13 aThe UCSB free-electron lasers provide kilowatts of continuously tunable radiation from 120 GHz to 4.8 THz. They have the most impact on terahertz science and technology that require a tunable, high power source to explore non-linear dynamics or that sacrifice incident power to recover the linear response of systems with very small cross-section. We describe three experiments that demonstrate the utility of these lasers in experiments on the terahertz dynamics of semiconductor nanostructures: (i) terahertz dynamics of resonant tunneling diodes, (ii) saturation spectroscopy of quantum wells and (iii) photon-assisted tunneling in superlattices.
1 aAllen, S., J.1 aCraig, K.1 aFelix, C., L.1 aGuimaraes, P.1 aHeyman, J., N.1 aKaminski, J., P.1 aKeay, B., J.1 aMarkelz, A., G.1 aRamian, G.1 aScott, J., S.1 aSherwin, M., S.1 aCampman, K., L.1 aHopkins, P., F.1 aGossard, A., C.1 aChow, D.1 aLui, M.1 aLiu, T., Y. uhttps://markelz.physics.buffalo.edu/node/25701623nas a2200205 4500008004100000020001400041245011600055210006900171260000800240300001200248490000600260520099500266100002001261700001801281700001801299700002001317700001501337700001601352856004901368 1994 eng d a0268-124200aSUBCUBIC POWER DEPENDENCE OF 3RD-HARMONIC GENERATION FOR INPLANE, FAR-INFRARED EXCITATION OF INAS QUANTUM-WELLS0 aSUBCUBIC POWER DEPENDENCE OF 3RDHARMONIC GENERATION FOR INPLANE cMay a634-6370 v93 aLarge third-order, free-carrier nonlinear susceptibilities, chi(3) (to approximately 0.2 esu), and subcubic dependence of the third-harmonic power on the incident intensity, have been observed between 19 cm-1 and 23 cm-1 for InAs/AlSb quantum wells with electron sheet densities between 2.5 x 10(12) cm-2 and 8 X 10(12) cm-2. We find that the transmission of the fundamental, and the samples' DC conductivity, decrease with increasing incident intensity, indicating a large rise in the scattering rate. Using the intensity-dependent transmission to account for absorption in the sample is not sufficient to recover a cubic power law for the third-harmonic intensity. In addition, given the increased scattering rate indicated by the conductivity data, the bulk free-carrier chi(3) due to non-parabolicity should decrease dramatically with increasing fundamental intensity, contrary to our results. Thus, non-parabolicity alone cannot account for the observed third-harmonic response.
1 aMarkelz, A., G.1 aAsmar, N., G.1 aGwinn, E., G.1 aSherwin, M., S.1 aNguyen, C.1 aKroemer, H. uhttps://markelz.physics.buffalo.edu/node/26700717nas a2200241 4500008004100000245008100041210006900122300001000191490000900201100002000210700001800230700001900248700001400267700001800281700001900299700001800318700001800336700002000354700002000374700001700394700001500411856004900426 1993 eng d00aFar-infrared nonlinear response of electrons in semiconductor nanostructures0 aFarinfrared nonlinear response of electrons in semiconductor nan a36-470 v18541 aSherwin, M., S.1 aAsmar, N., G.1 aBewley, W., W.1 aCraig, K.1 aFelix, C., L.1 aGaldrikian, B.1 aGwinn, E., G.1 aMarkelz, A.G.1 aGossard, A., C.1 aHopkins, P., F.1 aSundaram, M.1 aBirnir, B. uhttps://markelz.physics.buffalo.edu/node/320