Abstract

The optical and electrical properties of InAs quantum dots epitaxially grown on a silicon substrate have been investigated to evaluate their potential as both photodiodes and avalanche photodiodes (APDs) operating at a wavelength of 1300 nm. A peak responsivity of 5 mA/W was observed at 1280 nm, with an absorption tail extending beyond 1300 nm, while the dark currents were two orders of magnitude lower than those reported for Ge on Si photodiodes. The diodes exhibited avalanche breakdown at 22 V reverse bias which is probably dominated by impact ionisation occurring in the GaAs and AlGaAs barrier layers. A red shift in the absorption peak of 61.2 meV was measured when the reverse bias was increased from 0 to 22 V, which we attributed to the quantum confined stark effect. This shift also leads to an increase in the responsivity at a fixed wavelength as the bias is increased, yielding a maximum increase in responsivity by a factor of 140 at the wavelength of 1365 nm, illustrating the potential for such a structure to be used as an optical modulator.

© 2012 OSA

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Figures (5)

Fig. 1
Fig. 1

(a) Schematic of wafer structure. (b) TEM image of the wafer.

Fig. 2
Fig. 2

- Room Temperature responsivity of a 200 µm radius device (left axis, solid line) and photoluminescence spectra (right axis, dashed line) of the as grown samples.

Fig. 3
Fig. 3

(a) Dark current densities for 200, 100, 50 and 25 µm radius devices. The data is compared with Ge on Si and commercial InGaAs photodiodes. (b) Forward current characteristics of a 200 µm radius mesa diode.

Fig. 4
Fig. 4

(a) Avalanche gain data of a 200 µm radius diode measured using lasers with wavelengths of 1300 nm (symbols) and 633 nm (dashed line). (b) Dependence of photocurrent as a function of excitation power.

Fig. 5
Fig. 5

Responsivity curves from a 200 µm radius device at various reverse biases.

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