We review the applications of ion implantation in several III-V materials, and rapid thermal annealing techniques to activate the implant and remove the crystalline damage. Ion implantation has become the preferred technique when selective area doping is necessary. It has been used successfully to fabricate n, n+, p, p+, and semi-insulating regions in III-V binary, ternary, and quaternary compounds, and multilayer structures. Ion implantation has also been used to produce layer mixing in multilayer structures, and superlattice disordering. The annealing step necessary to activate the implant and remove the crystalline damage is complicated by several factors such as incongruent evaporation of the group V element, layer mixing, and dopant redistribution. Rapid thermal annealing techniques, which typically employ anneal times between 1 second and 100 seconds, are generally more suitable than conventional furnace annealing. The short annealing times result in much less dopant redistribution, and reduced layer mixing in multilayer structures. Even for short annealing times, it is necessary to employ a protection scheme to suppress the loss of the group V element. Several such methods are discussed, including dielectric encapsulation, proximity techniques, and controlled ambient techniques.

Ion implantation of Se+ and Zn+ ions into GaAs was carried out and characterization was performed by photoluminescence and Raman scattering at 2 K and room temperature, respectively. For comparison, implantation of Cd+ ions was also performed and further. a series of Si-doped GaAs samples were prepared by molecular beam epitaxy. In the Se+-implanted samples. with Se concentration between 1×1016 cm−3 and 5×1019 ca−3 the dominant radiative transition was the band-to-band emission, (B-B). No energy shift characteristic of (B-B) was observed but instead, the formation of a complex radiative center between donor impurities and implantation-induced damages, [D.LD] was revealed. This was in contrast to the Si-doped GaAs which displayed a pronounced energy shift of (B-B) towards higher energies with increasing Si concentration. The results suggest that (B-B) (reflecting the raising of the quasi Fermi-energy due to the increase of net free electron concentration) is significantly suppressed in the donor-ion implanted GaAs due to the presence of unremovable damages caused by implantation. In the Zn+ -implanted GaAs, the dominant emission was [g-g] which is formed just below the bound exciton emissions. The energy shift of [g-g] towards lower energies with increasing implanted Zn concentration was reproducibly observed. Thus clear differences in the PL spectra of donor- and acceptor-implanted samples were observed near the fundamental band edge. It was suggested that residual radiation damages suppress (B-B) but have little effect on acceptor-related emissions.

Epitaxial regrowth of deposited amorphous silicon has been previously described utilizing ion implantation amorphization, ion mixing and thermal anneal. This paper evaluates the effects of these process steps on crystalline quality utilizing Rutherford Backscattering (RBS), x-ray diffraction rocking curves and Raman scattering.

In situ (during implantation) regrowth results in defective crystallinity. In contrast, when there is no in situ regrowth, the post anneal crystallinity is equivalent by RBS and x-ray evaluation to virgin single crystal wafers. In situ regrowth is most pronounced during the high beam current ion mixing type implants which produce wafer temperatures of about 250°C. The final crystalline quality which results from different sequences of amorphization and ion mixing implants, is strongly dependent upon the amount of in situ regrowth which has occurred. The greater the in situ regrowth the poorer the final crystalline quality.

The defect and atomic profiles for MeV implantation of Si in GaAs were investigated using He++ channeling, TEM, and SIMS. Doses of 1–10 × 1015Si/cm2 at 1–3 MeV were used. MeV implantation at room temperature rendered only a small amount of lattice disorder in GaAs. Upon annealing at 400°C for 1 h or 800°C for 30 a, we observed a ‘defect-free’ surface region (- 1 μ for 3 MeV implant). Below this region, extensive secondary defects were formed in a band which was 0.7 μ wide and centered at 2 μ for 3 MeV implant. These defects were mostly dislocations lying in the [111] plane. SIMS depth profiles of Si implants showed the Si peak to be very close to the peak position of the defects. The experimental profiles of Si were compared to the TRIM calculation; generally good agreement existed among the peak positions.

Rapid thermal annealing has been used to study the electrical activation mechanisms for magnesium and selenium implants in GaAs. By analysing the changes in electrical activity as a function of annealing time and temperature, a model has been developed which accurately predicts the electrical properties following the post-implant annealing stage. The model has been used to study the activation of other ions, particularly zinc, beryllium, tin and sulphur, the results of which will be compared with those of magnesium and selenium. The results suggest that the mechanism for electrical activation is dominated by the diffusion of gallium, arsenic or vacancies. The paper will present the model and discuss the activation mechanisms of the ions.

Ion implantation has had a strong impact on the development of III-V strained-layer semiconductor (SLS) materials and device technologies. Implantation studies have helped delineate the present understanding of strained-layer stability and metastability limits. Resulting ion beam technologies have led to improvements in a variety of SLS discrete devices, including optoelectronic emitters, photodetectors, and field-effect transistors. Both SLS stability criteria and implanted SLS devices are reviewed with respect to future applications in optoelectronics.

In the Rapid-Thermal-Annealing of Si-implanted undoped semi-insulating GaAs three regimes are broadly identified. At ˜ 600°C, ion implantation damage is largely removed, as indicated by lattice-strain measurements performed by X-ray rocking curves. Between ˜ 600 – 900°C, “extended defects”, which presumably account for the long tails in the electron concentration depth profiles, are annealed. Higher annealing temperatures in this range result in profiles with successively shorter tails. Finally, beyond ˜ 900°C, “acceptor levels” in the material are revealed, which become effective in compensating the Si activation.

Effects of rapid thermal processing (RTP) on SiO2/GaAs interfaces have been investigated with Auger electron spectroscopy and X-ray photoelectron spectroscopy. SiO2 films of 100, 175, 200 and 1250 nm thickness have been deposited on liquid encapsulated Czochralski-grown (100) n-type GaAs wafers by the RF sputtering method. RTP has been performed at 800°C for 6 s. For comparison, conventional furnace processing (CFP) has also been performed at 800°C for 20 min for 200-nm-thick SiO2/GaAs. The Ga is observed on the outer SiO2 surface for RTP samples as well as CFP samples. This indicates that the outdiffusion of Ga occurs after only 6 s at 800°C even through 1250-nm-thick SiO2 films. The depth profile of Ga reveals the pile-up of Ga on the outer SiO2 surface for both RTP and CFP samples. The amount of Ga on the outer surface gradually increases in the thickness range 1250 to 175 nm. The As is also observed on the outer surface. The amount of Ga and As on the outer surface rapidly increases at 100 nm thickness. Electron traps in RTP samples have been studied with deep-level transient spectroscopy. Different electron traps are produced in GaAs by RTP between 100-nm- and 200-nm-thick SiO2/GaAs. It is thought that the production of different traps by RTP is related to the amount of Ga and As loss through SiO2 films from GaAs.

Using deep level transient spectroscopy we have studied the variations of electron traps in molecular beam epitaxial (MBE) AlxGa1−xAs by rapid thermal processing (RTP) using halogen lamps. RTP was performed at 700, 800 and 900 °C for 6s under a SiO2 cap and a capless condition. It is found that during RTP the electron traps with the thermal activation energies of 0.89 and 0.99 eV are produced in Al0.lGa0.9As and Al0.3Ga0.7As, respectively. The thermal activation energies of these traps are close to the reported ones for the trap EL2 in AlxGaM1−xAs. Therefore, these traps are probably related to the trap EL2. In the RTP samples under a capless condition, the concentrations of the trap EL2 in AlxGa1−xAs (x=0.1, 0.3) decreases from the surface to the deeper position in MBE layers, while the depth profile of the trap EL2 in GaAs is flat. It is suggested that the origin of the trap EL2 formation in AlxGa1−xAs is different from one in GaAs.

In this paper the fabrication process and characteristics of waveguides produced by He+ implantation in Y-cut X- and Z-propagating LiNbO3 are presented It is shown that low propagation losses, down to 1dB cm−1 at λ = 633μm can be obtained for TM modes only in Y-cut X-propagation samples whilst Y-cut Z propagating samples support both TE and TM modes with relatively low losses.

Effects of N-implantation on the composition depth profile, the chemical bonds and the optical transmittance of AlNx films have been investigated by means of Auger Electron Spectroscopy (AES), Fourier Transform Infrared (FT-IR) spectroscopy and visible transmission spectroscopy. AINx films were deposited on silicon (111) and commercial glass by an Activated Reactive Eyaporation (ARE) technique near room temperature. The 40 and 80 keV N+ -implantations were carried out at room temperature with doses ranging from 5×1016 to 5×1017 ions/cm2. The result of AES measurements revealed that the as-deposited AlNx film on Si consists of the AIN layer near the topsurface and the Al-rich layer near the interface. The concentration of nitrogen in the films increases as the N-dose increases up to 1×1017 ions/cm2. The N-implantation at a dose of 5×1017 ion/cm2 causes the interface between the film and the Si substrate to mix rather than increase the nitrogen concentration in the film. This higher dose implantation makes the FT-IR absorption peak corresponding to Al-N bonding become clear, and it makes the optical transmittance at a wavelength of 4400 Å go from 7% for as-deposited AINx film up to 70–90%. It is concluded that N-implantation into AlNx films causes the formation of AIN with a stoichiometric ratio to improve optical properties of the film.

In this paper the state-of-the-art in the use of dry etching for the fabrication of optoelectronic devices will be briefly reviewed, and to a lesser extent, the use of impurity-induced-disordering in these same structures will be discussed. In both instances, the author will rely heavily upon results from his own laboratory. This is being done in the interest of saving time and effort, although clearly at the risk of omitting some very important contributions from many others.

Ion beam assisted etching (IBAE) was used to define submicron structures into GaAs/AlGaAs and InP/InGaAsP heterostructures. Etch rates in excess of I pm/minute were obtained after optimization of the etching process, allowing the fabrication of optoelectronic structures which require smooth, vertical sidewalls and depths of several microns. By altering the gas flow and the ion beam parameters, the same technique was used to pattern electron beam-written structures with lateral dimensions of less than 30 nm and aspect ratios in excess of 5:1 in GaAs.

Laser-assisted dry etching of lithium niobate, LiNbO3, as well as other electro-optic materials could be an industrially important process in the fabrication of optical waveguides. In this investigation, an excimer laser (ArF; 193nm) was used to conduct etching reactions using nitrogen trifluoride, NF3. Enhancement of etching was observed by comparing the etch rate for a gas assisted process with that of a purely photoablative process. Chemical analysis of the etched features via Auger electron spectroscopy and correlation of a simple rate equation with the experimental data revealed that lasersurface interactions are responsible for the laser-assisted etching process.

Exposure of GaAs and AlGaAs to a hydrogen plasma has been shown to result in a significant change in the electrical and optical properties. The changes are related to the electrical deactivation of the deep and shallow impurities by hydrogenation. Spectroscopic and electrical measurements have shown that Si donors and C acceptors in high purity GaAs can be passivated by hydrogenation. Hydrogenation of p-type GaAs and AlGaAs has resulted in highly resistive material. SiO2 was found to be a suitable mask for the hydrogenation process. Single and multiple stripe geometry lasers have been fabricated by properly masking the laser structure. The lasers produced using the hydrogenation process have low threshold currents and are capable of cw room temperature operation.

We report temporal measurements of bandgap photoluminescence (PL) from GaAs surfaces under low-intensity CW laser excitation. We have observed slow PL degradation in n-type, p-type and semi-insulating (Cr-doped and LEC-grown) samples, and have fit the data to a simple power law. Calculations indicate a significant contribution from the bulk material, possibly via recombination-enhanced generation or migration of non-radiative centers. The effectiveness of various methods of surface treatment (photowashing, deposition of epitaxial AlGaAs, spin-coating with organic and inorganic sulfide films) has been assessed. One specific technique, involving coating with sodium sulfide, is effective in enhancing the PL efficiency and suppressing the degradation, but these effects are not permanent.

The passivation of GaAs MESFET's with PECVD silicon nitride films of both compressive and tensile stresses is reported. The shift of MESFET parameters due to passivation was found to be dependent upon gate orientation. For example, it is found that the shifts of threshold voltage are of opposite sign for MESFET's oriented along [011] and [011] directions. Our experiments show that nitride of tensile stress is preferable for MESFET's with [011] oriented gates. The shifts in VTH IDSS and GM of the devices before and after nitride passivation are lesd thaw s% if the nitride of appropriate stress states are used for passivation.

Breakdown voltage of the MESFET's after nitride deposition was also studied. It is found that the process with higher hydrogen incorporation tends to reduce the surface oxide and increase the breakdown voltage after nitride deposition.

Silicon dioxide films deposited on InP substrates are obtained in a reduced pressure, air and water cooled horizontal CVD reactor, with a rapid thermal heating. Deposition temperature as high as 700°C could be utilized with no degradation of the InP surface. At this temperature the resulting silicon dioxide films have excellent structural and electrical properties. MIS capacitors fabricated on InP substrates have been tested and a transistor behaviour has been observed on a first set of InP MISFETs. In situ processing for surface preparation prior to deposition can be utilized with this technique. A first attempt of in situ multiprocessing was carried on silicon substrates and is presented here.

Understanding metal/semiconductor contacts is important for the fabrication of device structures. To date most studies have been aimed at understanding the metallurgical or the electrical properties. Directly measuring the impurity concentrations immediately beneath a contact rather than inferring it from electrical measurements has up until now been difficult. This paper describes a backside SIMS technique which not only demonstrates the ability of measuring doping concentrations close to a metal/semiconductor contact but also is capable of measuring the consumption of semiconductor material during a metal/semiconductor reaction. The sample preparation technique can be used to enable backside profiling using other profiling techniques such as Auger and x-ray photoelectron spectroscopy depth profiling, Rutherford backscattering, and backside electrical evaluation. The Ge/Pd/GaAs solid phase ohmic contact is used to demonstrate the technique.

Contacts to GaAs substrates with n-type epilayers formed by GaAs/Ni/Ge/WN/Au, GaAs/Ni/Ge/Ni/WN/Au and GaAs/Ge/ Ni/WN/Au systems were investigated. Ohmic contacts in these systems were formed by a solid-phase reaction between Ni/Ge and GaAs. Interfacial reaction and electrical properties of these contacts are characterized by backscattering spectrometry, transmission electron microscopy and contact resistivity measurements. Resistivities in the 10−δ Ω cm range are achieved.