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The monolithic integration of III–V materials on silicon appears as the most promising, cost-effective, and versatile method for next-generation optoelectronic devices. Here, we report on GaAs metal-semiconductor-metal photodetectors integrated on an Si substrate by metal-organic chemical vapor deposition. The device architecture is based on a GaAs active layer grown on Si via ultrathin, low-temperature Ge buffer layers. The Ge-on-Si acts as a "virtual" substrate to reduce the overall structural defects in the GaAs device layers. The metal-semiconductor junction characteristics were optimized to effectively suppress the dark current and passivate the interface defects. This was achieved through the insertion of an ultrathin Al2O3 interlayer at the metal/GaAs interface. The results show that a Schottky barrier height of 0.62 eV and 0.8 eV for electrons and holes, respectively, can be achieved. Circular devices with diameters ranging from 30 to 140 μm were fabricated. The measured room temperature dark current is ∼48 nA for an applied reverse bias of 1.0 V and a device diameter of 30 μm. Additionally, the GaAs metal-semiconductor-metal structure exhibited a remarkable photoresponsivity and detectivity values of (0.54 ± 0.15) A/W and ∼4.6 × 1010 cm Hz1/2 W−1 at 5 V reverse bias, 850 nm, respectively. The proposed method offers great potential for the monolithic integration of GaAs on an Si platform. Furthermore, this technique can be extended to other III–V materials and lattice mismatched systems for high-performance multiple band optoelectronics. [ABSTRACT FROM AUTHOR]

A comprehensive study of different fundamental aspects of light emission from defects in Si semiconductor devices is described. With the help of a new highly sensitive spectroscopic photon emission microscope for continuous wavelength analysis, a unique assignment of the spectrum of the emitted light and the corresponding failure mechanism is established.

The origin of the substrate hole currents after gate oxide breakdown in metal-oxide-semiconductor field-effect transistor (nMosFET) devices is investigated, using spectroscopic and conventional photon emission microscopy. Spectral analysis of light from the breakdown locations, under positive gate bias, indicates that hot electrons mediate the light emitted from the breakdown spots. These hot electrons are generated by the high electric fields at the location of the breakdown. Furthermore, light emission due to substrate hole recombination with electrons injected from the gate through the leakage path (breakdown location) dominates the light emission spectrum under negative gate bias. This finding is further verified using carrier separation measurements. In these measurements, minority carrier currents induced by the light emitted at the breakdown location and measured at a remote pn junction are compared with the substrate hole currents before and after oxide breakdown. These measurements prove that under positive gate bias, the substrate hole current and the light emission from the breakdown locations, are dominated by hot electron impact ionization mechanism in the substrate. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]