Nonresonant carrier transport through high-field domains in semiconductor superlattices

Abstract

The actual Beld distribution in superlattices under electric field domain formation is investigated by photoluminescence and Raman spectroscopy. Prom the measured subband spacings, we determine the magnitude of the Beld that corresponds to resonant alignment of subbands in adjacent wells.The electron occupation of higher subbands is probed by photoluminescence (PL) measurements. Comparing the results of higher subband PL and the current-voltage characteristics, it is shown that the high-Beld domain is always nonresonantly coupled with a field strength below the resonance value. The sudden increase in the current when the high-field domain extends over the entire superlattice is explained. Calculations of the field distribution based on a microscopic model support our experimental observations.

Impact of interface roughness on perpendicular transport and domain formation in superlattices

“…1B which exhibits the usual sequence of branches [1,2]. In contrast to previous theoretical results the maximal current of the branches (90 µA) is significantly lower than the height of the first resonance.…”

“…This may yield complicated current-voltage characteristics exhibiting many branches due to the formation of domains with different electric fields inside the sample (see, e.g., [1] and references therein). These experimental features could be qualitatively reproduced by theoretical models combining the rate equations for the transport between the wells and Poisson's equation [2,3].…”

Semiconductor superlattices: a model system for nonlinear transport

“…Results for the superlattice studied experimentally in [123,124] (9 nm wide GaAs wells, 4 nm AlAs barriers, doping density N D = 1.5 × 10 11 /cm 2 , cross section A = 1.13 × 10 −4 cm 2 ) are shown in Fig. 11.…”

“…In contrast to the Gunn diode, semiconductor superlattices frequently exhibit the formation of stable stationary domains which lead to a characteristic saw-tooth pattern in the currentvoltage characteristic (see Fig. 21a) as observed by many different groups [16,17,123,124,[170][171][172][173][174]. (See also [175,176] for domain formation in a parallel magnetic field.)…”

Spectral modulation of exciton Fano resonance due to Zener breakdown in strongly biased superlattices

“…17 The effects of the Zener breakdown under a relatively strong bias on the WSL spectra and nonlinear transport, ͑i.e., the Bloch oscillation͒ resulting in negative differential resistance ͑NDR͒, were later discussed by many authors. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Hereafter, the resonant Zener tunneling between different energetically aligned subbands will be termed as Zener resonance or WSL resonance. Delocalized electron states in coupled WSL in biased SLs were first observed by photocurrent spectroscopy along with the measurement of the currentvoltage characteristics by Schneider et al 18 They observed the delocalization of electrons and anticrossing behavior ascribable to the nearest-and the second-nearest-neighbor resonant couplings induced by the Zener resonance.…”