Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 47: GaN on Si

HL 47.5: Vortrag

Mittwoch, 16. März 2011, 11:15–11:30, POT 51

Investigations of pn-junctions based on AlGaN / AlN structures for LEDs on Si(111) — •Antje Rohrbeck, Hartmut Witte, Phannee Saengkaew, Thomas Fey, Armin Dadgar, Jürgen Christen, and Alois Krost — nstitute of Experimental Physics, Otto-von-Guericke- University Magdeburg, Magdeburg, Germany

AlGaN/AlN - ultraviolet LEDs grown on Si(111) substrates are of high interest for many applications and have the advantages to easily be integrated within the silicon electronic. However, the large misfit between the AlGaN layers and the Si substrate introduces many defects in the layers. The most important part of the AlGaN/AlN-LED structure is the p- AlGaN / n-AlGaN junction involving the AlGaN/GaN multi-quantum well. We have investigated these pn-junctions within the LED structure grown by MOVPE in detail and n-type AlGaN layers as well as p-type AlGaN/p-type GaN multilayer which were grown separately. All AlGaN layers have an Al content of 10 % and the Si(111) substrates were highly n-type doped. For these investigations Hall-effect measurements, CV- and IV-characteristics, impedance spectroscopy, surface scanning potential and scanning capacitance microscopy were used. The p-type doping of the AlGaN/GaN multilayer structure shows a Mg-accumulation at the AlGaN/GaN interfaces. Furthermore, there are negative differential capacitances and currents within the CV- and IV-characteristics whose origins will be discussed considering the impact of surface defects or the AlGaN/GaN interfaces. Additionally, electroluminescence spectra of the whole LED structure give further indications that defects are located within or close to the pn-junctions.