Photoluminescence measurements on GaN/AlGaN modulation doped quantum wells
- PDF / 228,374 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 67 Downloads / 234 Views
Internet Journal Nitride Semiconductor Research
Photoluminescence measurements on GaN/AlGaN modulation doped quantum wells J. Dalfors1, J. P. Bergman1, P.O. Holtz1, B. Monemar1, H. Amano2 and I. Akasaki2 1Department 2Department
of Physics and Measurement Technology, Linköping University, of Electrical and Electronic Engineering, Meijo University,
(Received Friday, May 28, 1999; accepted Friday, July 30, 1999)
Photoluminescence spectra were measured for 100 Å wurtzite GaN AlGaN modulation doped quantum wells. Three well-resolved peaks originate from the quantum well. The theoretically calculated confinement energies have been compared to the experimental energy positions and found to be in good agreement with the data, assuming that the piezoelectric field is largely screened by the electron gas. The highest energy transition may originate from the Fermi edge, consistent with the temperature dependence of the photoluminescence. Decay times for the different transitions indicate that the photoexcited holes are localized.
1
Introduction
2
There has recently been an increasing interest in IIInitrides, partly due to their promising properties for high power microwave devices; e.g. modulation doped fieldeffect transistors (MODFETs) [1], [2]. By doping of the barrier layer close to a hetero-interface, i.e. modulation doping, charge transfer across the interface occurs and the electrons form a two-dimensional electron gas (2DEG) in the approximately triangular shaped potential in the active layer close to the interface. Since these electrons are spatially separated from the donor impurities in the barriers, they should have a relatively high mobility. This is an important property utilized in devices such as high electron mobility transistors (HEMTs). Optical and electrical properties in these kind of structures have been extensively investigated, especially in the GaAs/AlGaAs [3], [4], but also in the InGaAs/InP [5], [6] materials system. The interest on the III- nitride side has so far mostly been focused on GaN/AlGaN modulation doped heterostructures [7], [8], [9], [10]. The understanding of the electronic structure and transitions involving the 2DEG is still limited, however. To the best of our knowledge, no detailed optical investigations have been done on modulation doped GaN/AlGaN quantum wells (QWs) [11]. Therefore, further investigations of these structures are necessary to achieve a proper understanding of the physical properties of this system, in order to exploit the full benefits of the high potential this materials system offers.
Samples and experimental procedure
We have performed photoluminescence (PL) and time resolved PL (TRPL) on modulation doped GaN/AlGaN QW samples. Two similar structures have been investigated, with nearly identical optical spectra. Detailed results for one of these structures are discussed below. The experimentally observed luminescence from confined states in the well has been compared with simple theoretical predictions. The samples were grown by metal organic vapor phase
Data Loading...
