Electroluminescence in dopant-free GaAs/AlGaAs single heterojunctions: 2D free excitons, H-band, and the tidal effect

N. Sherlekar; S. R. Harrigan; L. Tian; B. Cunard; Y. Qi; B. Khromets; M. C. Tam; H. S. Kim; Z. R. Wasilewski; J. Baugh; M. E. Reimer; F. Sfigakis

arXiv · 2601.10081

Electroluminescence in dopant-free GaAs/AlGaAs single heterojunctions: 2D free excitons, H-band, and the tidal effect

N. Sherlekar·S. R. Harrigan·L. Tian·B. Cunard·Y. Qi·B. Khromets·M. C. Tam·H. S. Kim·Z. R. Wasilewski·J. Baugh·M. E. Reimer·F. Sfigakis

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Abstract

Bright electroluminescence (EL) from dopant-free ambipolar lateral p-n junctions in GaAs/AlGaAs single heterointerface (SH) heterostructures is used to probe neutral free excitons arising from two-dimensional electron and hole gases (2DEGs and 2DHGs). The EL spectra reveal both the heavy-hole neutral free exciton (X$^0$) and the high-energy free exciton of the H band (HE). A combination of transition energies, lifetimes, spatial emission profiles, and temperature dependences points to a predominantly two-dimensional character for these excitons at the SH. For X$^0$, the EL peak energies (1515.5-1515.7 meV) lie slightly above the corresponding bulk GaAs photoluminescence (PL) line at 1515.3 meV, while time-resolved measurements yield markedly shorter lifetimes for EL than for PL (337 ps vs. 1610 ps), consistent with recombination in a confined interfacial layer. The HE exciton exhibits a Stark blueshift under forward bias below threshold, and its energies and lifetimes (down to 575 ps) are tuned by the topgate voltage; above threshold, HE emission is quenched in favor of X$^0$. Finally, the tidal effect $-$ a form of pulsed EL generated by swapping the topgate voltage polarity in ambipolar field-effect transistors $-$ produces an X$^0$ line at the same energy as in the lateral p-n junction and reproduces the characteristic nonmonotonic frequency dependence of the brightness previously observed in quantum-well heterostructures, again indicating a 2D-like origin. Taken together, these results show electrically generated and controllable 2D-like excitons (HE and X$^0$), thereby bridging 2D exciton physics and 2DEG/2DHG platforms in dopant-free GaAs/AlGaAs SH devices.

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N. Sherlekar, S. R. Harrigan, L. Tian, B. Cunard, Y. Qi, B. Khromets, M. C. Tam, H. S. Kim, Z. R. Wasilewski, J. Baugh, M. E. Reimer, F. Sfigakis. 2026-01-15. Electroluminescence in dopant-free GaAs/AlGaAs single heterojunctions: 2D free excitons, H-band, and the tidal effect. https://arxiv.org/abs/2601.10081

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