Issue
EPL
Volume 88, Number 4, November 2009
Article Number 46002
Number of page(s) 6
Section Condensed Matter: Structural, Mechanical and Thermal Properties
DOI http://dx.doi.org/10.1209/0295-5075/88/46002
Published online 03 December 2009
EPL, 88 (2009) 46002
DOI: 10.1209/0295-5075/88/46002

The formation of a charge layer at the interface of GaMnAs and an organic material

Wenjin Chen1, Baikui Li1, Hongtao He1, Jiannong Wang1, Hoi Lam Tam2, Kok Wai Cheah2, Xiancun Cao3, Yuqi Wang3, Guijun Lian4 and Guangcheng Xiong4

1   Department of Physics, The Hong Kong University of Science and Technology Clear Water Bay, Kowloon, Hong Kong, China
2   Department of Physics, Hong Kong Baptist University - Kowloon, Hong Kong, China
3   Institute of Solid State Physics, Chinese Academy of Sciences - Hefei, Anhui 230031, China
4   Department of Physics, Peking University - Beijing 100871, China


received 16 June 2009; accepted in final form 8 November 2009; published November 2009
published online 3 December 2009

Abstract
The interface formed between the ferromagnetic semiconductor GaMnAs and the organic semiconductor N,N$^\prime $-diphenyl-N,N$^\prime $-bis(1-naphthyl)(1,1$^\prime $-biphenyl)-4,4$^\prime $-diamine (NPB) was investigated using current transport measurement and ultraviolet photoemission spectroscopy (UPS). The hole injection barrier at a GaMnAs and NPB interface was measured as 0.77 eV by modelling the measured current density-voltage (J-V) characteristics in a GaMnAs/NPB/Al structured device. The vacuum level shift at a GaMnAs/NPB interface was deduced to be 0.54 eV, indicating that a dipole layer exists at the interface. A UPS study gave a vacuum level shift of 0.53 eV and a band offset between the GaMnAs valence band and the highest occupied molecular orbital of NPB of 0.79 eV, in good agreement with the results of J-V measurements. We attribute the vacuum level shift to charge transfer across the interface.

PACS
68.35.-p - Solid surfaces and solid-solid interfaces: structure and energetics.
73.40.-c - Electronic transport in interface structures.
79.60.-i - Photoemission and photoelectron spectra.

© EPLA 2009