Four-terminal structures are fabricated by focused-ion-beam (FIB) scanning on an AlGaAs/ InGaAs/GaAs modulation doped structure. The large carrier density of this system results in small depletion spreading and a 260-nm-square four-terminal structure is successfully formed. The bend resistance of this structure indicates that ballistic coupling between two facing terminals remains up to room te...

We have measured the carrier spin dynamics in p-doped InAs/GaAs quantum dots by pump-probe and time-resolved photoluminescence experiments. We obtained experimental evidence of the hyperfine interaction between hole and nuclear spins. In the absence of an external magnetic field, our calculations based on dipole-dipole coupling between the hole and the quantum dot nuclei lead to a hole-spin dep...

Strong electric-field transients resonant to intersubband transitions in n-type modulation-doped GaAs/AlGaAs quantum wells induce coherent Rabi oscillations, which are demonstrated by a phase-resolved measurement of the light emitted by the sample. The time evolution of the intersubband polarization is influenced by Coulomb-mediated many-body effects. The subpicosecond period and the phase of t...

We study the dynamics of the charged and neutral excitons in a modulation-doped GaAs quantum well by time-resolved photoluminescence under a resonant excitation. The radiative lifetime of the charged exciton is found to be surprisingly short, 60 ps. This time is temperature independent between 2 and 10 K, and increases by a factor of 2 at 6 T. We discuss our findings in view of present theories...

Photoluminescence studies of neutral and charged excitons in modulation doped GaAs/Al0.3Ga0.7As quantum wells are performed as functions of applied pressure, temperature, and excitation power and frequency. Varying both pressure and incident power allows sensitive selection of the different exciton transitions. The G±X crossover in the barriers at 7 to 9 kbar accelerates photo-pumping of electr...

We present a surface passivation method that reduces surface-related losses by almost two orders of magnitude in highly miniaturized GaAs open microcavity. The microcavity consists curved dielectric distributed Bragg reflector (DBR) with radius $\sim 10$ $\mu$m paired GaAs-based heterostructure. heterostructure semiconductor DBR followed an n-i-p diode layer quantum dots the intrinsic region. F...

Green light-emitting device (LED) based on Er:Ga 2 O 3 /GaAs heterojunction was fabricated in this work. Erbium (Er) doped Ga film prepared p -GaAs substrate by pulsed laser deposition. The structural, morphological and optical properties were investigated X-ray diffraction, atomic force microscope photoluminescence. Bright green electroluminescence dominated 524 549 nm peaks can be observed wi...

We present results on the experimental and theoretical investigations of metal contacts on chalcogen passivated GaAs(1 0 0) surfaces. Photoemission spectroscopy investigations show that depending on the metal used for the contact formation the chalcogen passivation reduces the interaction between metals and GaAs(1 0 0). For Sb no chemical reaction at all with the substrate surface is found, whi...

This work reports fabrication details of heterojunction diodes and solar cells obtained by sputter deposition of amorphous GaAs on p-doped single crystalline Si. The effects of two additional process steps were investigated: A hydrofluoric acid (HF) etching treatment of the Si substrate prior to the GaAs sputter deposition and a subsequent annealing treatment of the complete layered system. A t...

We demonstrate a new, nonlinear optical effect of electric currents. First, a steady current is generated by applying a voltage on a doped GaAs crystal. We demonstrate that this current induces second-harmonic generation of a probe laser pulse. Second, we optically inject a transient current in an undoped GaAs crystal by using a pair of ultrafast laser pulses and demonstrate that it induces the...