Zero-dimensional excitonic properties of self-organized quantum dots of CdTe grown by molecular beam epitaxy

Abstract

The successful growth of self-organized quantum dots (QDs) of CdTe on ZnTe (100) surface by molecular beam epitaxy is reported. Atomic force microscope measurements on the uncapped samples revealed the formation of CdTe QDs with typical dot diameters of 20±2 nm and heights of 2.7±0.3 nm at 3.5-ML-thick CdTe deposited. The intensity of photoluminescence (PL) from the capped QDs was higher than CdTe/ZnTe single quantum wells (SQWs) by a few orders of magnitude at 4.2 K, and exhibited a thermal quenching with an activation energy of 110 meV, which is about twice as large as those in SQWs. In time-resolved PL measurements, the decay time was almost independent of temperature below 20 K. This is interpreted as due to the zero-dimensional excitonic properties in QDs.

Anisotropic spin dynamics of confined electrons in CdTe/ZnTe quantum structures

“…Indeed, it is known as the main mechanism of the thermal quenching of the excitonic PL in CdTe/ZnTe QDs and QWs. 16,17 In our QD sample, the PL intensity begins to decrease around 50 K, and it is less than the maximum by almost 2 orders of magnitude at T = 100 K. 9 The temperature characteristic of the PL is consistent with the critical temperature of the onset of the electron-spin precession shown in Fig. 2.…”

“…It is also possible that the inhomogeneity of the isotropic exchange ␦, on which the exciton beat frequency depends, affects the exciton signal decay. What we can state safely is that the signal lifetime is not limited by the recombination of excitons because the exciton PL lifetime exceeds 100 ps at temperatures lower than 50 K. 9 The observation of the quantum beat between the bright exciton states ͉Ϯ1͘ becomes difficult when the exciton signal decays so fast because their splitting by anisotropic exchange interaction is usually very small. 23 As the temperature rises and comes close to 200 K, the absolute signal intensity of ⌬⌰ K ͑t͒ decreases, and the signal- to-noise ratio falls in both the QD and the QW samples.…”

“…This is suggested by the photoluminescence ͑PL͒ peak energy which is considerably higher than expected from the above dot size. 9 The areal density of the QDs was estimated to be 8 ϫ 10 10 cm −2 . The spin dynamics is optically observed by the TRKR measurements.…”

“…The detail of the fabrication procedure is described elsewhere. 9 In both the samples, the growth of CdTe layers was performed by an alternate deposition of Cd and Te fluxes on ZnTe ͑100͒ surfaces. Under some appropriate conditions, 1/2 monolayer ͑ML͒ of CdTe is grown at each cycle of the alternate deposition in an autoregulated manner.…”

Volmer-Weber growth of CdTe on silicon: a one-dimension Monte Carlo model

“…The greater part of the processes used to grow these structures are governed by the transition from twoto three-dimensional growth regime driven by the strain energy accumulated in the epitaxial layer [1][2][3][4][5][6][7], the StranskiKrastanow (SK) growth mode. Ferreira et.…”