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In this letter, we create a path to remove excess carriers in the base region of a SiGe phototransistor (HPT) by introducing the trap centers. The behavior of the trap centers in the SiGe heterojunction bipolar transistor (HBT) is a form of nonideal (nkT) base current. The responsivity of the device is 0.43 A/W with fully SiGe HBT-compatible device structure to facilitate the integration of the following amplification circuitry. The full-width at half-maximum of the pulse is 90 ps and the tail of the optical pulse response is largely reduced with the nkT current. By reducing the tail, bandwidth is increased from 1.5 to 3 GHz. This proposes SiGe HPT is applicable for optoelectronic technology.

A simple and complementary metal-oxide-semiconductor-compatible method for fabricating germanium ͑Ge͒ single-electron transistors (SETs) is proposed, in which the Ge quantum dots (QDs) are naturally formed by selective oxidation of Si 0.95 Ge 0.05 / Si wires on a silicon-on-insulator substrate. Clear Coulomb-blockade oscillations, Coulomb staircase, and negative differential conductances were experimentally observed at room temperature. The tunneling currents through the Ge QDs were simulated by the Anderson model with two energy levels. Analysis of the current-voltage characteristics indicates that the single-electron addition energy of the Ge QD is about 125 meV.

Room-temperature electroluminescence at 1.3 and 1.5 μm from Ge/Si quantum-dot light-emitting diodes is reported. The devices were fabricated in a mesa-type structure, with a silicon oxide layer on the top for surface/sidewall passivation. Different passivation processes were employed. We found that the integrated electroluminescence intensities were relatively less sensitive to temperature, persisting at nearly the same intensity up to RT. The fabricated device shows an internal quantum efficiency of about 0.015% at RT. The improved emission property is attributed to the reduced nonradiative recombination centers due to the surface passivation and thermal treatment.

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