Friday, November 20, 2009, 11:00 am — Small Seminar Room, Bldg. 510
InxGa1-xN alloys have acquired a considerable importance for optoelectronics and photonics, mainly due to their direct bandgap, which is tunable from 0.7 eV to 3.4 eV depending on alloy composition. The high piezoelectric fields present in nitride heterostructures and the lack of a suitable substrate characterize the development of the devices based on this material family. InxGa1-xN alloys are being currently used for several applications such as the fabrication of green-blue-violet light emitting diodes (LEDs), violet laser diodes (LDs), solar cells and visible light photodetectors [1]. The increasing interest on the application of this alloy to fabricate integrated fluorescence sensors motivates this work. This talk summarizes the effort carried out on the growth by plasma-assisted molecular beam epitaxy of InGaN bulk layers and multiple quantum well (MQW) heterostructures to fabricate visible and near-UV photodetectors [2].
The growth-regimes of the alloy have been completely described as a function of the growth conditions (impinging fluxes and substrate temperature), what allows to predict layer morphology from the initial conditions. A complete characterization of the InGaN bulk layers has been carried out in order to understand the properties of this alloy: Phase separation, electron accumulation at the surface and InN losses due to thermal decomposition have been described as a function of alloy composition.
Metal-insulator-semiconductor structures on InGaN, metal-semiconductor structures on p-type InGaN:Mg and MQW based photodetectors have been examined in order to improve the rectification properties of the contacts fabricated on InGaN and to increase photodetector response in photovoltaic mode. It is also shown how the proper design of the structures can allow us to increase photocarrier collection efficiency in two orders of magnitude, or to achieve photovoltaic response in apparently symmetric structures.
Hosted by: Ivan Bozovic
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