Abstract
In-plane photoconductivity (PC) measurements in a GaN/AlN quantum dots
(QDs) layer show a TM-polarized infrared (IR) peak, at 0.9 eV, and a
visible-UV (vis-UV) peak, at 2.8 eV. Based on the energy and
polarization dependence, the 0.9 eV is associated with the polarized S
to Pz intraband transition within the QDs. The IR PC turns from positive
PC (PPC) to negative PC (NPC) as temperature is raised, increasing
exponentially from 50 to 300 K. Vis-UV radiation renders PPC at all
temperatures. Combined with vis-UV radiation, the IR PC is negative even
at low temperatures. Based on these observations, we suggest a model in
which IR excited carriers in the QD layer are coupled to deep levels
(DLs) in the AlN barrier and turn immobile, i.e., NPC is observed.
Vis-UV radiation re-excites them into the QDs, resulting in PPC. At
lower temperatures coupling into the DL becomes inefficient, thus, IR
excitation results in PPC. This model was translated into rate
equations. Simulations based on these rate equations reproduce well the
experimental results.
Original language | English GB |
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Article number | 104512 |
Journal | Journal of Applied Physics |
Volume | 108 |
Issue number | 10 |
DOIs | |
State | Published - 1 Nov 2010 |
Externally published | Yes |
Keywords
- aluminium compounds
- gallium compounds
- III-V semiconductors
- infrared spectra
- photoconductivity
- polarisation
- semiconductor quantum dots
- ultraviolet spectra
- visible spectra
- wide band gap semiconductors
- Photoconduction and photovoltaic effects
- Quantum dots
- III-V and II-VI semiconductors
- Semiconductors