Defects, structure, and chemistry of InP–GaAs interfaces obtained by wafer bonding

Abstract

We have examined the crystallographic structure of GaAs/InP interfaces obtained by wafer fusion following different procedures. Plan-view and cross-sectional transmission electron microscopy reveal that the interface is not only composed of a regular array of two sets of edge dislocations and is more complex than generally supposed. If a twist is created due to misalignment of the two substrates, the dislocations are not edge dislocations but also have a screw component. Dislocations for which the Burgers vectors have a component normal to the interface are also present. Those dislocations probably result from steps and some of them accommodate the tilt between the two substrates. Inclusions and voids as well as a low number of volume dislocations are present in all the samples. The observed volume dislocation density near the interface lies in the 105–107 cm−2 range and these volume dislocations may be associated with thermal mismatch. The origin of all these defects is discussed.

Microstructure of GaAs/GaN interfaces produced by direct wafer fusion

“…The average separation between dislocations of this network depends on the magnitude of the strain, which needs to be relaxed. Networks of such dislocations have been reported in the literature for the InP/GaAs system [8,13]. They are usually observed at some distance from the interface and the average separation between dislocations measured in this system was of the 5 order of a few micrometers.…”

“…Its thickness varied between 5-10 Å in samples bonded at 750°C and 15-20 Å in the one bonded at 550°C. Thin layers of residual native oxide have previously been observed in other systems of bonded materials [8,9], both by TEM and by Secondary Ion Mass Spectroscopy of the fused interface. We also confirmed the presence of oxygen at the GaAs/GaN bonded interface by detailed energy dispersive X-ray (EDX) analysis.…”

“…As in the case of GaAs/InP or GaN/sapphire bonded materials, these cavities were asymmetric, extended primarily into one 3 material only. In the case of the InP/GaAs the cavity always extended more deeply into the InP side [8,10], while cavities formed at the fused GaAs/sapphire interface formed almost entirely in the GaAs and revealed distinct faceting on (001) and (111)-type GaAs planes [11,12]. In these GaAs/GaN samples, the cavities extended almost entirely into the GaAs.…”

“…These dislocations were formed in the GaAs, since they are parallel to either the [110] GaAs or the [1][2][3][4][5][6][7][8][9][10] GaAs direction.…”

Optical Power Transmission Through Adhesive and Bonding Layers

“…For polarization, the transmission coefficient decreases steadily as a function of , but reflection remains small up to (unless the index contrast is high). The reflection is generally stronger for polarization than for polarization, where it is partially suppressed due to Brewster's effect: for incidence, at the Brewster angle, , one has [from (15)] and the transmission (which equals unity for ). For nonmatching layers there is a second Brewster angle, , corresponding to the wave in layer 2, propagating at the angle .…”