Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 7: III-V semiconductors I

HL 7.8: Talk

Monday, March 26, 2007, 12:45–13:00, H17

Comparison of the electronic band formation and band structure of GaN_xAs_1−x and GaN_xP_1−x — •Martin Güngerich¹, Wolfram Heimbrodt¹, Gerhard Weiser¹, Bernardette Kunert¹, Kerstin Volz¹, Peter Jens Klar², and John Franz Geisz³ — ¹Fachbereich Physik und Wissenschaftliches Zentrum für Materialwissenschaften, Philipps-Universität, Renthof 5, D-35032 Marburg, Germany — ²I. Physikalisches Institut, Justus-Liebig-Universität, Heinrich-Buff-Ring 16, D-35392 Gießen, Germany — ³National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401, USA

Incorporation of an increasing amount of N into GaAs causes a strong red shift of the fundamental band gap (E₋) which is accompanied by the blue shift of a higher lying band of N impurity states (E₊). This repulsive behaviour is successfully parameterized by a phenomenological two-level band-anticrossing (BAC) model. In GaP:N the energetic ordering of host and impurity states is reversed compared to GaAs:N because the localized levels lie within the host band gap. We show that the simple BAC model fails to describe the evolution of the lowest conduction states in GaN_xP_1−x. Photocurrent and electromodulated reflection measurements of GaN_xP_1−x support a BAC-related blue shift of its E₊ band which in this material originates from the GaP-like lowest direct band gap. On the other hand, electromodulated absorption and pressure-dependent photoluminescence studies indicate that the wide energy distribution of the lower-lying N-related states leads to an anticrossing interaction involving many N levels.