Electroluminescence and photoluminescence excitation study of asymmetric coupled $\mathrm{Ga}\mathrm{As}∕{\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ V-groove quantum wires

We have studied systems of asymmetric coupled GaAs V-groove quantum wires $p\text{−}i\text{−}n$ diodes, in which the electrons and holes are injected into different wires. Despite the use of a $7\mathrm{nm}$ thick AlGaAs tunnel barrier, and although we demonstrate that holes tunnel more slowly than electrons, we observe a very efficient and fast tunneling between the quantum wires (QWR’s). We attribute this to the achievement of a resonance between hole levels in the two QWR’s. Photoluminescence excitation experiments are compared with accurate calculations of the excitonic absorption yielding a level of carrier transfer of nearly 100%. Temperature-dependent electroluminescence exhibits clear effects of tunneling up to room temperature but cannot distinguish separate electron/hole tunneling from exciton tunneling.

Figure 1

Cross-sectional TEM micrograph of the QWR region in sample A with a schematic illustration of the electron and hole injection via the VQW’s.

Figure 2

(a) and (b) Schematic illustration of energy level alignment and the electrical carrier injection in samples A and B, respectively.

Figure 3

(a) and (b) Low temperature $(T=15\mathrm{K})$ EL and polarized PLE spectra of samples A and B, respectively. The main EL peak for sample A (B) has maximum at the absolute energy $1.595\mathrm{eV}\left(1.590\mathrm{eV}\right)$. (c) Calculated polarized excitonic absorption spectra for the $w$-QWR only (fine lines) and the total absorption of the two QWR’s (bold lines). Dashed lines correspond to polarization perpendicular to the QWR axis, while solid lines are for parallel polarization.

Figure 4

Room-temperature EL spectra compared with (unpolarized) low-temperature PLE spectra of (a) sample A and (b) sample B. The three dashed curves below the three EL peaks $I_1^w$, $I_2^w$, and $I_1^n$ are obtained by a fitting procedure. According to the calculations, $I_2^w$ consists of two subpeaks, shown with dotted curves below $I_2^w$.

Figure 5

Arrhenius plots of the intensity ratios $I_1^w∕I_2^w$ (circles) and $I_1^w∕I_1^n$ (squares) for (a) sample A and (b) sample B, respectively. The high-temperature data follows a linear dependence, shown by the dotted lines, corresponding to the activation energies shown in the figure.