Energy level spectroscopy of InSb quantum wells using quantum-well LED emission

Abstract

We have investigated the low-temperature optical properties of InSb quantum-well ͑QW͒ light-emitting diodes, with different barrier compositions, as a function of well width. Three devices were studied: QW1 had a 20 nm undoped InSb quantum well with a barrier composition of Al 0.143 In 0.857 Sb, QW2 had a 40 nm undoped InSb well with a barrier composition of Al 0.077 In 0.923 Sb, and QW3 had a 100 nm undoped InSb well with a barrier composition of Al 0.025 In 0.975 Sb. For QW1, the signature of two transitions ͑CB1-HH1 and CB1-HH2͒ can be seen in the measured spectrum, whereas for QW2 and QW3 the signature of a large number of transitions is present in the measured spectra. In particular transitions to HH2 can be seen, the first time this has been observed in AlInSb/InSb heterostructures. To identify the transitions that contribute to the measured spectra, the spectra have been simulated using an eight-band k . p calculation of the band structure together with a first-order time-dependent perturbation method ͑Fermi golden rule͒ calculation of spectral emittance, taking into account broadening. In general there is good agreement between the measured and simulated spectra. For QW2 we attribute the main peak in the experimental spectrum to the CB2-HH1 transition, which has the highest overall contribution to the emission spectrum of QW2 compared with all the other interband transitions. This transition normally falls into the category of "forbidden transitions," and in order to understand this behavior we have investigated the momentum matrix elements, which determine the selection rules of the problem.

Regression Analysis for Transport Electron Scattering Caused by Structural Defects in InSb Quantum Wells: Application of Matthiessen's Formula

“…Transmission electron microscopy (TEM) analyses showed that microtwins (MTs) and threading dislocations (TDs) are dominant structural defects in InSb QWs grown on GaAs(001) substrates, [2][3][4] which are common choices of substrates for InSb-QW-based devices. [5][6][7][8][9][10][11] These defects degrade the total electron mobilities in InSb QWs. 4,12,13) Based on regression analyses for Matthiessen's law, recently we have reported quantitative studies for electron scattering due to both TD and MT defects in InSb QWs, 12,13) although the effect of these defects on electron transport in InSb epilayers [14][15][16][17][18][19] and non-InSb two-dimensional (2D) systems [20][21][22][23][24][25] which include QW structures has long been investigated.…”

Efficiency droop in InSb/AlInSb quantum-well light-emitting diodes

“…We have previously obtained estimated values of the effective carrier temperature in the QWLEDs, at low temperature and under net bias, of 105 K and 129 K for QW2 and QW3, respectively, 17 corresponding to carrier energies of approximately 10 meV. In comparison, the energy difference between the lowest electron subband and the barrier conduction band is approximately 20 meV and 45 meV for QW2 and QW3, respectively (at low temperature under net bias).…”

“…The bandstructure of the devices (calculated using an eight-band kÁp model) can be found in Ref. 17. The very small electron effective mass ($0.014 m o ) in InSb, approximately one fifth that in GaAs, leads to strong quantum confinement even in relatively wide quantum wells.…”

“…This system is attractive for realizing mid-infrared optoelectronic components, [12][13][14] both for use in applications such as components for non-dispersive infrared gas sensing, 15 but also as a way of exploiting the quantum effects arising from the very small electron mass. 16,17 Although the factors limiting the efficiency of narrow bandgap LEDs have been studied extensively over the last couple of decades, 18 there have been very few reports and analysis of efficiency droop. For example, Krier 19 and Das and Tobin 20 observed efficiency droop in InAs heterostructure and interband cascade Type IIsuperlattice based LEDs, respectively, but only when the devices were driven with long pulses, suggesting that heating was the origin of the droop.…”

“…In comparison, the energy difference between the lowest electron subband and the barrier conduction band is approximately 20 meV and 45 meV for QW2 and QW3, respectively (at low temperature under net bias). Carrier-carrier scattering could, therefore, lead to carriers escaping from the quantum wells (particularly at low temperatures where transitions involving higher subbands contribute to the overall emission spectrum 17 ). In addition, the observed temperature dependence of the droop, with the current at which maximum emission occurs increasing with increasing temperature, is consistent with the recent analysis of the temperature dependence of droop in GaN-based diodes using the DADR model.…”