Colloidal quantum dot active layers for light emitting diodes Jennifer G. Pagan a,b, * , Edward B. Stokes a,c , Kinnari Patel a , Casey C. Burkhart a , Michael T. Ahrens b , Philip T. Barletta b , Mark O’Steen d a The University of North Carolina at Charlotte, Charlotte 28223-001, NC, USA b Dot Metrics Technologies, Charlotte 28223-001, NC, USA c Center for Optoelectronics and Optical Communications, Charlotte Research Institute, UNC Charlotte, Charlotte 28223-001, NC, USA d Veeco Compound Semiconductor Inc., St. Paul 55127, MN, USA Received 15 April 2006; accepted 13 June 2006 The review of this paper was arranged by Prof. A. Zaslavsky Abstract In this paper the preliminary results of incorporating a novel active layer into a GaN light emitting diode (LED) are discussed. Inte- gration of colloidal CdSe quantum dots into a GaN LED active layer is demonstrated. Properties of p-type Mg doped overgrowth GaN are examined via circular transmission line method (CTLM). Effects on surface roughness due to the active layer incorporation are exam- ined using atomic force microscopy (AFM). Electroluminescence of LED test structures is reported, and an ideality factor of n = 1.6 is demonstrated. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: LED; Quantum dot; CdSe; Heterostructure 1. Introduction Nanotechnology is proliferating at a rapid rate in many areas including semiconductor lasers, biotechnology, and optoelectronics, as researchers create applications which capitalize on the unique advantages afforded them by oper- ating on the nanoscale. In the case of semiconductor lasers it was found that by creating active layers on order of the de Broglie wavelength in all spatial directions, the move- ment of the free electrons would be restricted. This electron confinement inhibits the spreading of carriers thereby reducing the thermal sensitivity of a device. In fact thermal effects should be zero when electrons are three dimension- ally confined. In such a system the density of states is defined as a delta function resulting in a larger and nar- rower gain profile for the laser [1,2]. Quantum dots are the closest representation of a semiconductor system where there is three dimensional carrier confinement. The emis- sion spectrum of a quantum dot can be tuned across a wide range of wavelengths due to the quantum size effect, mak- ing the technology ideal for use in light emitting diode (LED) active layers [3]. Semiconductor materials from the III to V group are used in high-efficiency LEDs at both ends of the visible spectrum, III-Arsenide–Phosphide (III- AsP) materials provide emission from yellow to infrared, and III-Nitride (III-N) materials emit from blue to green into the ultraviolet. Some III-Nitride LEDs contain nano- scale inhomogeneities or ‘‘quantum dots’’ which consist of high indium fraction InGaN, and appear naturally during MOCVD growth of InGaN active layers [4].There is no material in either the III-AsP or III-N material systems that provides efficient deep green (555–585 nm) emission. Highly efficient deep green colloidal CdSe quantum dot emitters are available however, and it has been recently 0038-1101/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.sse.2006.06.009 * Corresponding author. Address: Dot Metrics Technologies, Charlotte 28223-001, NC, USA. Tel.: +1 704 687 2727. E-mail address: jpagan@dotmetricstech.com (J.G. Pagan). www.elsevier.com/locate/sse Solid-State Electronics 50 (2006) 1461–1465