Effects of interdiffusion on the band alignment of GeSi dots

Abstract

The interdiffusion effects on the band alignment of the GeSi dots embedded in Si matrix were studied by temperature- and excitation-power-dependent photoluminescence measurements. A different power-dependent behavior of the photoluminescence for the as-grown and the annealed samples was observed. It was suggested that the band alignments of the dots changed from type II to type I after annealing due to the Ge/Si interdiffusion. The decrease of the valence band offset, which was also induced by the Ge/Si interdiffusion, was observed from the temperature-dependent photoluminescence measurements.

Excitation power-independent photoluminescence of inverted quantum hut structures embedded in SiGe superlattice

“…Self-assembled growth of the IQH structures with SiGe alloying within Si (001) lattice reduces the strain considerably and hence reduces the conduction band offset [17]. Hence, position of PL of the IQH structures was found to be independent of excitation power as has been observed previously in annealed Ge quantum dot samples [7]. The thermal activation energy for the IQH related peak can be calculated by following equation [18]:…”

“…But pseudomorphic growth of Ge (having 4% bigger lattice parameter than Si) quantum dots on Si (001) surface and subsequent capping with Si generate inherent interfacial strain in these materials [4,5]. The presence of strain at the interface of Ge quantum dot and Si (001) lattice leads to complicated energy-band alignment hindering development of efficient silicon based optical materials as transition remains Type-II, showing strong dependence of photoluminescence (PL) on excitation power [6][7][8][9][10]. Here we show that Ge inverted quantum hut structures grown within Si (001) crystals reduce importance of the interfacial strain and exhibit strong PL whose energy remains almost independent of the excitation power.…”

Optical properties of individual site-controlled Ge quantum dots

“…5 Recent progress in site-controlled growth of SiGe QDs on pre-patterned Si(001) substrates, [6][7][8][9][10] and their commensurable embedding into photonic crystal slabs 11 has opened a unique route toward deterministic positioning of individual SiGe QDs in photonic crystal resonators. Yet, optical studies were mainly performed on ensembles of SiGe QDs, which cause broadening of the photoluminescence (PL) lines due to variations in QD size [12][13][14][15][16] and local composition. 17 Spectroscopy on single QDs appears to be a domain of III-V [18][19][20] and II-VI 21,22 heteromaterials, whereas optical measurements on isolated group-IV nanostructures were only reported for dispersed porous-Si grains 23 and Si pillars in an oxide matrix.…”

Miniband-related 1.4–1.8 μm luminescence of Ge/Si quantum dot superlattices

“…For the type-II Ge/ Si heterostructures the values of u ranged from 13 to 22 [37,80,81,94]. The II-I type conversion has been reported for the GeSi structures having strong intermixing in the annealed QDs [37] and in WL [80] with u % 1. Our QDSLs had u-factors less than 3 for low excitation densities (u = 2.5 for P £ 6 W cm -2 in Fig.…”

“…This fact, however, cannot be the reason for the observed red shift of the QDSL PL peak either. Available experimental data on the activation energy for the QD PL band in Ge/Si structures are very controversial and scattered between 15 meV and 183 meV [9,12,26,37]. It is noteworthy that only values between 21 meV and 46 meV are attributed to the electron subsystem in Ref.…”