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Register a new userEpitaxial InGaAsP/InP photodiode for registration of InP scintillation
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Operation of semiconductor scintillators requires optically-tight integration of the photoreceiver system on the surface of the scintillator slab. We have implemented an efficient and fast quaternary InGaAsP pin photodiode, epitaxially grown upon the surface of an InP scintillator wafer and sensitive to InP luminescence. The diode is characterized by an extremely low room-temperature dark current, about 1 nA/cm2 at the reverse bias of 2 V. The low leakage makes possible a sensitive readout circuitry even though the diode has a large area (1 mm/times1 mm) and therefore large capacitance (50 pF). Results of electrical, optical and radiation testing of the diodes are presented. Detection of individual alpha-particles and gamma-photons is demonstrated.
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One of the solutions enabling performance progress, which can overcome the downsizing limit in silicon technology, is the integration of different functional optoelectronic devices within a single chip. Silicon with its indirect band gap has poor optical properties, which is its main drawback. Therefore, a different material has to be used for the on-chip optical interconnections, e.g. a direct band gap III-V compound semiconductor material. In the paper we present the synthesis of single crystalline InP nanodots (NDs) on silicon using combined ion implantation and millisecond flash lamp annealing techniques. The optical and microstructural investigations reveal the growth of high-quality (100)-oriented InP nanocrystals. The current-voltage measurements confirm the formation of an n-p heterojunction between the InP NDs and silicon. The main advantage of our method is its integration with large-scale silicon technology, which allows applying it for Si-based optoelectronic devices.
Transport properties of holes in InP nanowires were calculated considering electron-phonon interaction via deformation potentials, the effect of temperature and strain fields. Using molecular dynamics, we simulate nanowire structures, LO-phonon energy renormalization and lifetime. The valence band ground state changes between light- and heavy-hole character, as the strain fields and the nanowire size are changed. Drastic changes in the mobility arise with the onset of resonance between the LO-phonons and the separation between valence subbands.
We show that the morphology of the initial monolayers of InP on Al0.48In0.52As grown by metalorganic vapor-phase epitaxy does not follow the expected layer-by-layer growth mode of lattice-matched systems, but instead develops a number of low-dimensional structures, e.g., quantum dots and wires. We discuss how the macroscopically strain-free heteroepitaxy might be strongly affected by local phase separation/alloying-induced strain and that the preferred aggregation of adatom species on the substrate surface and reduced wettability of InP on AlInAs surfaces might be the cause of the unusual (step) organization and morphology
We have studied the emission properties of individual InAs quantum dots (QDs) grown in an InGaAsP matrix on InP(100) by metal-organic vapor-phase epitaxy. Low-temperature microphotoluminescence spectroscopy shows emission from single QDs around 1550 nm with characteristic exciton-biexciton behavior, and a biexciton antibinding energy of more than 2 meV. Temperature-dependent measurements reveal negligible optical-phonon induced broadening of the exciton line up to 50 K, and emission from the exciton state clearly persists above 70 K. Furthermore, we find no measurable polarized fine structure splitting of the exciton state within the experimental precision. These results are encouraging for the development of a controllable photon source for fiber-based quantum information and cryptography systems.
Regular arrays of InP nano pillars have been fabricated by low energy Electron Cyclotron Resonance (ECR) Ar+ ion irradiation on InP(111) surface. Several scanning electron microscopy (SEM) images have been utilized to invetsigate the width, height, and orientation of these nano pillars on InP(111) surfaces. The average width and length of these nano-pillars are about 50 nm and 500 nm, respectively. The standing angle with respect to the surface of the nano-pillars depend on the incidence angle of the Ar ion irradiation during the fabrication process. Interestingly, the growth direction of the nano pillars are along the reflection direction of the ion beam and the standing angles are nearly same as the ion incidence angle with the surface normal. This nano-pillas are easily transferred from the InP surface to double sided carbon tape without any damage. High Resolution Transmission Electron Microscopy (HRTEM) study of single nano-pillar reveals that this nano-pillar are almost crystalline in nature except 2-4 nm amorphous layer on the outer surface. The transmission electron microscopy combined with energy-dispersive x-ray spectroscopy (TEM-EDS) analysis of these nano pillars exhibit that the ratio of In and P is little higher compared to the bulk InP.
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