Capacitance studies of multilayer ensembles of InAs QDs in a GaAs matrix
- PDF / 363,509 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 70 Downloads / 142 Views
DIMENSIONAL SYSTEMS
Capacitance Studies of Multilayer Ensembles of InAs QDs in a GaAs Matrix A. A. Gutkin^, P. N. Brunkov, and S. G. Konnikov Ioffe Physicotechnical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia ^e-mail: [email protected] Submitted March 14, 2007; accepted for publication March 28, 2007
Abstract—Quasi-static capacitance characteristics of multilayer arrays of vertically coupled InAs quantum dots (QDs) in a GaAs matrix were analyzed on the assumption of a Gaussian energy distribution of the ground state of the QDs. An array of InAs QDs with a characteristic base size of about 20 nm and height of ~3 nm was ordered in the growth direction and had 3, 6, or 10 layers spaced by ~5 nm. It was found that, as the number of layers increases from 3 to 10, the average binding energy of the ground electron state grows from ~80 to ~120 meV and the root mean square deviation characterizing the energy distribution of the levels of this state decreases from ~30 to ~15 meV. PACS numbers: 68.65.Hb, 73.21.La, 73.63.Kv DOI: 10.1134/S1063782607110115
The development of new electronic and optoelectronic devices based on self-assembled quantum dots (QDs) embedded in a semiconductor matrix requires a detailed study of the electrical properties of such ensembles and of methods for control over their properties. In particular, of considerable interest is the manner in which the electronic structure of vertically coupled QDs varies as the number of QD layers in the semiconductor matrix increases. According to theoretical and experimental studies [1–3], the interaction between the electron states of QDs lying in different layers has the result that the levels associated with these states are split and their energy decreases. The related spectral shift of the low-temperature photoluminescence (PL) associated with recombination of electron– hole pairs in InAs QDs embedded in a GaAs matrix was observed in [1–3]. Another important characteristic of the QD array that determines the possibility of its use is the depth of an electron level in a QD relative to the edge of the respective allowed band in the matrix (carrier binding energy in a QD). The variation of this quantity in multilayer arrays depends on numerous factors and fundamentally differs from the spectral shift of radiative recombination in QDs, because carriers of
both signs are involved in the recombination process. It has been shown previously that the energy spectrum of states in QDs can be studied by analysis of capacitance characteristics of Schottky barriers with a QD layer built in to their space charge region (SCR) [4, 5]. This paper reports the results of capacitance studies of multilayer arrays of vertically coupled InAs QDs embedded in n-GaAs. The structures under study were grown by molecular-beam epitaxy on the (001) plane of n-GaAs substrates. The InAs QD array was ordered in the growth direction and comprised 3, 6, or 10 layers spaced by ~5 nm. Each layer was formed via transformation of an elastically strained InAs layer with a
Data Loading...
