The formation of GaAs/Si photodiodes by pulsed-laser deposition

Abstract

Hetero-pairing of thin-film GaAs on Si is of considerable interest for novel applications in optoelectronics. However, the formation of high-quality GaAs is difficult and requires expensive top technologies such as molecular beam epitaxy (MBE) and related methods. In general, MBE forms high-quality epitaxial layers but is not capable of the straightforward formation of GaAs on Si because of the 4.1% lattice mismatch between both materials. We have developed and explored the possibilities of pulsed-laser deposition (PLD) for the formation of GaAs films on (100) ntype Si substrates. The films have been produced in vacuum (10 -6 torr) employing the fundamental (1064 nm), second (532 nm), and third (355 nm) harmonic emission of a Nd:YAG laser with a repetition rate of 10 Hz and a pulse duration of 6 ns. The laser was focused on (100) p-type (10 19 cm -3 ) GaAs wafers with an energy fluence of 0.79-0.84 J/cm 2 . During the deposition, the substrate was not heated. The current-voltage characteristic of the samples showed rectification, i.e., the doping of the GaAs target was successfully maintained in the PLD film and a diode was formed in conjunction with the oppositely doped Si substrate. The observation of photocurrent without bias is an additional proof that an operating junction was achieved. The crystallographic quality of the films was checked by x-ray analysis and revealed that the films show [111]-oriented crystalline parts. The realization of GaAs/Si photodiodes reveals the potential of PLD to be used for the monolithic integration of GaAs photonic devices with Si circuits.

Photosensitive hetero-pairing of p-GaAs/n-Si by pulsed-laser deposition

“…Apparently, ultraviolet PLD causes a different GaAs/Si interface morphology than the other two employed laser lines. We already speculated in a previous work that the interface morphology depends on the PLD line employed [9]. Concerning hetero-device engineering, this work introduces PLD as an undemanding versatile method to form GaAson-Si devices for optoelectronic applications.…”

“…Although first attempts already took place in the 1980s [5], the formation of GaAs-on-Si with PLD is, in comparison with MBE and MOCVD, considerably lesser exploited and almost no data were available when we started our activities. Meanwhile, we have demonstrated that nanosecond PLD forms photosensitive thin-film GaAs on glass and Si [6][7][8][9] and that the films can be used for novel all-optical logic operations [10,11].…”

Electronic properties of p-GaAs deposited on n-Si with pulsed-laser deposition

“…We are aware of only one paper [5] containing data on GaAs-on-Si PLD before we started to work on the subject four years ago. Meanwhile, we demonstrated that PLD of p-type GaAs onto counter-doped Si produces a technologically appealing photo-responsive hetero-pair with sensitive bias dependence [6][7][8][9]. In the current work, we emphasize the dynamic rectification properties and the doping features of p-GaAs/n-Si structures formed with PLD at 355, 532, and 1064 nm.…”

“…The flux and ablation time combinations resulted in film thicknesses of 300 nm, 600 nm, and 180 nm, for the ablation at 355 nm, 532 nm, and 1064 nm, respectively. The electric contacts have been realized in the same way as in [6][7][8][9], i.e., with vacuum evaporated Al on the GaAs layer and with sliver paste to the substrate. The dynamic rectification capabilities of the samples were checked with alternating current (AC) measurements at room temperature without illumination.…”

X-ray, absorption and photocurrent properties of thin-film GaAs on glass formed by pulsed-laser deposition

“…This clearly established orientation opens the possibility to lower the costs for certain MBE and MOCVD based processes by using PLD GaAs on glass as wafer material instead of bulk material. Meanwhile, Raman investigations of the film surface have shown that the films consist of microcrystallites embedded in a predominantly amorphous texture [16]. Since the crystals are spread out uniformly over the film surface, the x-ray picks up their (111) orientation.…”