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GROWTH AND OPTOELECTRONIC CHARACTERISATION OF II-VI BLUE-EMITTING MATERIALS

Objective


The optimum precursors combination for the growth of ZnSe, ZnSSe and ZnMgSSe has been identified as Me2Zn(NEt3), t-Bu2Se, t-Bu2S and (MeCp)2Mg. By the use of a nitrogen plasmas, or the nitrogen-containing precursors Zn[N(SiMe3)2]2 and EtZnN(SiMe3)2, nitrogen has successfully been incorporated into ZnSe at the level of approx. 1E17 am{-3}. However, the layers did not show p-type conductivity due to compensation of the nitrogen by n-type impurities (chloride) or passivation by hydrogen. Lattice-matched ZnMgSSe was successfully grown as GaAs and quantum-size effects were observed. Optical and electron beam pumped blue green lasers at room temperature were also demonstrated.
Semiconductors based on II-VI materials are of special interest in the field of optoelectronics : their very large bandgaps span the electromagnetic spectrum from the red to the blue, allowing great flexibility.

ZnSe/GaAs heterostructures and multiple-quantum wells(MQW)based on ZnSSe/ZnSe are particularly suited for use in devices operating in the blue region of the visible spectrum. Thus, they are excellent candidates for fabricating blue-emitting lasers and LEDs for applications in high-density optical memories, display devices, medical diagnostics, and communications through salt-water and ice.

Serious problems hinder the production of these devices: it has been almost impossible to control the type of conductivity exhibited by II-VI semiconductors. For example, ZnSe can be grown to exhibit n-type conductivity but not p-type; this is a serious drawback, as one needs both conductivity types to construct p.n.-diodes and electrically driven laser diodes.

The consortium will study the mechanisms of ZnSe growth by MOVPE: fundamental understanding of the physical principles controlling the properties of MOVPE-grown material will be acquired. Also, systematic research towards obtaining device quality p-and n-type material will be conducted. This achievement will be a significant advance beyond the state-of-the art, as, thus far, only expensive, non production-oriented MBE technologies have been successfully employed for ZnSe based device fabrication.

The quality of the grown material will be assessed by novel optical and electrical methods. Appropriate precursors for layer growth at low temperatures and for p-type doping, which are currently unavailable, will be researched and synthesised.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Epichem Ltd
Address
Power Road Bromborough
L62 3QF Wirral
United Kingdom

Participants (4)

QUEEN MARY AND WESTFIELD COLLEGE - UNIVERSITY OF LONDON
United Kingdom
Address
Mile End Road
EN1 4NS London
Rheinisch-Westfälische Technische Hochschule Aachen (RWTH)
Germany
Address
Sommerfeldstraße 24
52074 Aachen
UNIV AVEIRO
Portugal
Address
Campo Universitario
3800 Aveiro
UNIV LIEGE
Belgium
Address
Institut De Physique - Sart Tilman
4000 Liege