Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 44: Quantum dots: Preparation and characterization

HL 44.10: Talk

Wednesday, March 18, 2015, 12:00–12:15, EW 203

Towards site-controlled In(Ga)As quantum dots at telecom wavelengths — •Caterina Clausen, Matthias Paul, Marc Sartison, Jan Kettler, Michael Jetter, and Peter Michler — Institut für Halbleiteroptik und Funktionelle Grenzflächen and Research Center SCoPE, Universität Stuttgart, Allmandring 3, 70569 Stuttgart, Germany

Single photon sources and sources of entangled photon pairs play one main part in quantum cryptography and quantum information technologies. The emission wavelength of 1310 nm correspond to the telecom O-band. In this range the dispersion and absorption of optical fibers is minimal. This characteristic is needed for loss free transmission in present communications networks. Semiconductor quantum dots (QDs) are excellent candidates for such applications due to very good optical properties and low area densities. The advantage of site-controlled grown QDs is simple integration into devices . The studied structures are produced by metal-organic vapor-phase epitaxy on exactly oriented GaAs substrates. The strain surrounding the QDs is reduced by a In₁₀Ga₉₀As layer directly over the InGaAs-QDs. This leads to actual larger QDs, reduces the effective band gap, and shifts the emission to higher wavelengths. For the growth of positioned QDs, GaAs substrates are pre-structured with a hexagonal hole pattern. A GaAs buffer layer ensures a (100) growth surface in the etched holes. Then the QD material is deposited. It is possible to influence the nucleation in the holes by choosing the right growth parameter.