Microscopic Basis for the Mechanism of Carrier Dynamics in an Operatingp−nJunction Examined by Using Light-Modulated Scanning Tunneling Spectroscopy

Abstract

The doping characteristics and carrier transport in a GaAs p-n junction were visualized with a 10 nm spatial resolution, using light-modulated scanning tunneling spectroscopy. The dynamics of minority carriers under operating conditions, such as recombination, diffusion, and electric field induced drift, which had previously been analyzed on the basis of empirical electric properties, were successfully examined on the nanoscale. These results provide a solid basis for elucidating the mechanism of the carrier transport properties predicted by using the macroscopic analysis.

Real-space imaging of transient carrier dynamics by nanoscale pump–probe microscopy

“…In STM on a semiconductor, a nanoscale metal-insulator-semiconductor (MIS) junction is formed by the STM tip, tunneling gap, and sample. Thus, when a reverse bias voltage is applied to the junction, tip-induced band bending (TIBB) occurs in the surface region owing to the leakage of the electric field into the sample [9,18,21]. With optical illumination, the redistribution of photocarriers reduces the electric field and changes the surface potential, which is called SPV, and increases the effective bias voltage applied to the tunnel junction.…”

“…Its spatial resolution, however, is generally limited by wavelength, and information is inevitably averaged over the nanoscale components, despite that they are organized with the greatest care to produce desired functions. In contrast, the real space observation of atomic-scale structures by scanning tunneling microscopy (STM) has lifted the veil from various longstanding problems and is extending the frontiers of science and technology [4][5][6][7][8][9]. However, since the temporal resolution of STM is limited to less than 100 kHz because of the circuit bandwidth, the target carrier dynamics has been beyond its field of vision.…”

Probing nanoscale potential modulation by defect-induced gap states on GaAs(110) with light-modulated scanning tunneling spectroscopy

“…Since the GaAs͑110͒ surface has no surface state within the bulk band gap, TIBB easily occurs at positive sample bias voltages, while it scarcely occurs at negative bias voltages. 12 A negative sample bias voltage of −1.7 V, at which no photocurrent was detected, was chosen as a set point for LM-STS measurements. In the positive-sample-bias-voltage region, the tunneling current oscillates owing to the illumination with a chopped laser light, and the two virtual I-V curves, which correspond to those under dark ͑blue͒ and under light ͑red͒ conditions, are simultaneously obtained.…”

Laser-Combined STM and Related Techniques for the Analysis of Nanoparticles/Clusters

“…The addition of optical technologies to STM provides new approaches to the study of nanoscale-material physics and chemistry. Nearfield optical microscopy (NSOM) and other techniques [78][79][80][81][82][83][84][85][86], which have not been discussed in this chapter, are expected to play complementary roles in understanding and developing the physics and chemistry of new nanoparticles/clusters for realizing novel functional devices.…”