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QUATERNARY NITRIDE LOW-THRESHOLD LASER

Objective

The III-nitride semiconductor laser diodes (LDs) lag significantly behind their GaAs counterparts in terms of performance. One of the major reasons for the counter-performance of nitride LDs is the presence in the active region of giant polarization-induced electric fields. Following some very encouraging results obtained in an initial assessment phase, we propose here to do finalizing assessment work in order to demonstrate that device quality InAlGaN heterostructures can be grown and offer a viable solution to this problem, by eliminating these polarization fields from the LD active region and hence improving all basic performance characteristics of nitride LDs. The III-nitride semiconductor laser diodes (LDs) lag significantly behind their GaAs counterparts in terms of performance. One of the major reasons for the counter-performance of nitride LDs is the presence in the active region of giant polarization-induced electric fields. Following some very encouraging results obtained in an initial assessment phase, we propose here to do finalizing assessment work in order to demonstrate that device quality InAlGaN heterostructures can be grown and offer a viable solution to this problem, by eliminating these polarization fields from the LD active region and hence improving all basic performance characteristics of nitride LDs.

OBJECTIVES
The ultimate objective of this project is the significant improvement of nitride laser diodes (LDs) by using in the LD active region InAlGaN heterostructures with significantly-reduced internal electric field. Such LDs should exhibit reduced lasing threshold, increased output power and enhanced device lifetime. For the short assessment period, the general objective is to show the feasibility of this innovative approach, by demonstrating nearly-zero electric field InAlGaN heterostructures with improved lasing characteristics. Specifically, in this period we will:O1 Assess the material properties of selected quaternary InAlGaN alloy thin films and quantum well (QW) heterostructures grown by RF-MBE. O2 Perform initial growth and material assessment experiments of MOVPE-grown InAlGaN. O3 Demonstrate nearly-zero electric field InAlGaN/GaN QWs. O4 Show in optical pumping experiments that the nearly-zero field InAlGaN/GaN QWs have lower lasing threshold compared to equivalent GaN/AlGaN or InGaN/GaN QWs.

DESCRIPTION OF WORK
The work can be partitioned in three technical workpackages:
WP1: MATERIAL PROPERTIES OF InAlGaN THIN FILMS AND HETEROSTRUCTURES. InAlGaN quaternary thin films and InAlGaN/GaN quantum well (QW) heterostructures will be grown mainly by RF-MBE. Exploratory growth experiments will be performed also with MOVPE. The quaternary alloys will have 10-40% Al and 0-15%In. Systematic material characterization of InAlGaN films and QW heterostructures of selected quaternary composition will address questions about residual doping, alloy clustering and inhomogeneities, dislocation densities in QW heterostructures, and strain relaxation.

WP2: ZERO-FIELD InAlGaN/GaN QUANTUM WELLS. A series of InAlGaN/GaN QW samples, with the Al-concentration in the range 10-40% and the In-concentration in the range 0-15%, will be fabricated and characterized with the aim to demonstrate that for a given quaternary composition the field in InAlGaN/GaN QWs cancels. The electric field measurement in the QW layers will be achieved by optical methods.

WP3: ZERO-FIELD QUATERNARY LASER STRUCTURE:
A laser cavity with the active region consisting of a nearly-zero electric field quaternary heterostructure, as determined in WP2, will be fabricated and its lasing properties will be characterized with optical pumping experiments. These results will be compared with a reference laser cavity containing a non-zero electric field in the active QWs, in order to demonstrate that when quaternaries are used in the active region of nitride LDs we can achieve significantly lower lasing thresholds.

Funding Scheme

ACM - Preparatory, accompanying and support measures

Coordinator

FOUNDATION FOR RESEARCH AND TECHNOLOGY - HELLAS
Address
Vassilika Vouton
71110 Iraklio, Crete
Greece

Participants (2)

COMMISSARIAT A L'ENERGIE ATOMIQUE
France
Address
31-33 Rue De La Federation
75752 Paris Cedex 15
UNIVERSITAET STUTTGART
Germany
Address
Keplerstrasse 7
70174 Stuttgart