Damage In InP Research Articles

Ion beam induced damage in InP during heavy-ion elastic recoil detection analysis

Heavy-Ion Elastic Recoil Detection Analysis (HIERDA) is an analytical technique which has undergone rapid development in the past few years with the availability of high-energy Tandem accelerators for materials science applications. HIERDA has found application in the study of various semiconductor systems, particularly III–V compounds. The technique employs a high-energy heavy-ion analysing beam to knock constituent nuclei from the target material and a time of flight and energy (ToF-E) detector system to extract mass and depth of origin information from these recoiling nuclei. Present work examines the sample damage produced in InP under typical analysis conditions. The depth distribution of damage induced by an 127I analysing beam of varying energy (54–98 MeV) and dose (10 13−2 × 10 14 ions/cm 2) in InP has been examined using RBS channelling, and cross-sectional TEM.

Investigation of the annealing behavior of damage in Si implanted InP by photoacoustic and Raman spectroscopy

The annealing behavior of damage in InP implanted with 200 keV Si ions at doses of 10 12–10 16 ions/cm 2 was investigated by photoacoustic spectroscopy (PAS) using a microphone as a detector and Raman spectroscopy. Band tails were observed in the photoacoustic (PA) spectra of implanted samples at energies lower than the bandgap energy. The PA intensity at the band tails increased with increasing implantation dose and reached a critical value at a dose of 10 14 ions/cm 2 indicating that the implanted layers were completely amorphized. The isochronal (15 min) annealing curves of the PA intensity for the amorphized samples can be classified into four temperature regions: region I below 200°C, region II at 200–300°C, region III at 300–600°C and region IV above 600°C. The results of PA and Raman measurements indicated that the implanted layers were in an amorphous state in region I, the implanted layers transformed from an amorphous state to a mono-crystalline state including complicated defects in region II, the defects decreased slightly in region III and defects with the dissociation of phosphorus from the sample surface were generated in region IV.

Comparing ion damage in GaAs and InP

In this paper, we study argon ion damage in both GaAs and InP. Low temperature photoluminescence measurements of GaAs and InP multiple quantum well (MQW) heterostructures are compared before and after an argon ion bombardment of 500 eV. Computer simulations of the channeling depth and atomic displacement in both materials are also calculated using SCattering of Heavy, Low Energy Ions into CHannels (SCHLEICH). We demonstrate that the range of ion damage in the InP MQW structure appears to be greater than in the GaAs structure and the results from the computer simulations confirm and support these experimental findings.

Raman-scattering assessment of Si+-implantation damage in InP

We studied the lattice damage caused by Si+ implantation into semi-insulating InP, with doses in the range of 1012 to 5×1014 cm−2, and the subsequent lattice recovery achieved by rapid thermal annealing (RTA), by means of Raman spectroscopy. With increasing implantation dose, an intensity reduction of the first- and second-order Raman peaks characteristic of crystalline InP is observed, together with the enhancement of disorder-activated modes. In samples implanted with doses higher than 1014 cm−2 the Raman spectra resembles that of amorphous InP, and the samples can be considered as fully amorphized. By RTA at 875 °C for 10 s, sample crystallinity is recovered, even in the case of those samples implanted with the highest dose. After annealing, the Raman spectra show no evidence of disorder-activated modes, and the intensity of the characteristic second-order peaks approaches the value found in unimplanted InP.

Room temperature damage removal from InP by optical pumping

Removal of ion-implantation-induced damage in InP is observed to a considerable extent by optical pumping using argon ion laser irradiation at room temperature. The damage takes the form of recombination, scattering, and compensation centers, which were generated by Be implantation with dose of 1010–1012/cm2. We find that minority carrier injection by optical pumping is an attractive alternative to technologies based on a thermal annealing approach for the removal of these centers.

Room-temperature annealing of Si implantation damage in InP

Spontaneous recovery at 295 K of Si implant damage in InP is reported. InP(Zn) and InP(S) wafers of (100) orientation have been implanted at room temperature with 600 keV Si+ ions to doses ranging from 3.6×1011 to 2×1014 cm−2. Room-temperature annealing of the resultant damage has been monitored by the Rutherford backscattering/channeling technique. For Si doses ≤4×1013 cm−2, up to 70% of the initial damage (displaced atoms) annealed out over a period of ≊85 days. The degree of recovery was found to depend on the initial level of damage. Recovery is characterized by at least two time constants t1<5 days and a longer t2≊100 days. Anneal rates observed between 295 and 375 K are consistent with an activation energy of 1.2 eV, suggesting that the migration of implant-induced vacancies is associated with the reordering of the InP lattice.

Ion milling damage in InP and GaAs

Near-surface damage created by Ar+ ion milling in InP and GaAs was characterized by capacitance-voltage, current-voltage, photoluminescence, ion channeling, and transmission electron microscopy. We find no evidence of amorphous layer formation in either material even for Ar+ ion energies of 800 eV. Low ion energies (200 eV) create thin (≤100 Å) damaged regions which can be removed by annealing at 500 °C. Higher ion energies (≥500 eV) create more thermally stable damaged layers which actually show higher backscattering yields after 500 °C annealing. Heating to 800 °C is required to restore the near-surface crystallinity, although a layer of extended defects forms in GaAs after such a treatment. No dislocations are observed in InP after this type of annealing. The electrical characteristics of both InP and GaAs after ion milling at ≥500 eV cannot be restored by annealing, and it is necessary to remove the damaged surface by wet chemical etching. For the same Ar+ ion energies the damaged layers are deeper for InP than for GaAs after 500 eV ion milling at 45° incidence angle. Removal of ∼485 and ∼650 Å from GaAs and InP, respectively, restores the initial current-voltage characteristics of simple Schottky diodes.

Ion Milling Damage in InP and GaAs

ABSTRACTNear-surface damage created by Ar+ ion milling in InP and GaAs was characterized by capacitance-voltage, current-voltage, photoluminescence, ion channeling and transmission electron microscopy. We find no evidence of amorphous layer formation in either material even for Ar+ ion energies of 800eV. Low ion energies (200eV) create thin (≤100 Å) damaged regions which can be removed by annealing at 500°C. Higher ion energies (≤500 eV) create more thermally stable damaged layers which actually show higher backscattering yields after 500°C annealing. Heating to 800°C is required to restore the near-surface crystallinity, although a layer of extended defects forms in GaAs after such a treatment. No dislocations are observed in InP after this type of annealing. The electrical characteristics of both InP and GaAs after ion milling at ≥500 eV cannot be restored by annealing, and it is necessary to remove the damaged surface by wet chemical etching. For the same Ar+ ion energies the damaged layers are deeper for InP than for GaAs-after 500 eV ion milling at 45° incidence angle, removal of ∼485 Å and ∼650 Å from GaAs and InP respectively restores the initial current-voltage charaeteristics of simple Schottky diodes.

Effects of impurities on radiation damage in InP

Strong impurity effects upon introduction and annealing behavior of radiation-induced defects in InP irradiated with 1-MeV electrons have been found. The main defect center of 0.37-eV hole trap H4 in p-InP, which must be due to a point defect, is annealed even at room temperature. Its annealing rate is found to be proportional to the 2/3 power of the preirradiation carrier concentration in InP. Moreover, the density of the hole trap H5 (Ev+0.52 eV) in p-InP, which must be due to a point defect–impurity complex, increases with increase in the InP carrier concentration. These results suggest that the radiation-induced defects in InP must recover through long-range diffusion mediated by impurity atoms. A model is proposed in which point defects diffuse to sinks through impurities so as to disappear or bind impurities so as to form point defect–impurity complexes. In addition to the long-range diffusion mechanism, the possibility of charge-state effects responsible for the thermal annealing of radiation-induced defects in InP is also discussed.

Comparison of calculated depth distributions of implanted ions for genuine and Ge-substituted InP targets

Abstract Both MARLOWE-based computer simulation and transport theory have been used to evaluate the depth distributions of ion range and damage in InP assuming diatomic or monoatomic (Ge-substituted) targets. Results indicate that the mean depth and straggling in both distributions are higher for the diatomic target but deviations are less than 10–15% for the cases studied: N, Zn and Bi ions in the energy range of 10 to 40 keV.

Injection-enhanced annealing of InP solar-cell radiation damage

This paper demonstrates that minority-carrier injection due to forward bias and light illumination under low current density and short-time injection conditions at room temperature can lead to enhanced recovery of radiation-induced defects in p-InP and radiation damage in InP n+-p junction solar cells. Deep-level transient spectroscopy analysis shows that the major defect centers H4 (EV +0.37 eV) and E2 (EC −0.19 eV) in p-InP exhibit injection-enhanced annealing which is a recombination-enhanced effect with a reduced activation energy of 0.133 eV. The marked recovery of the InP n+-p solar-cell radiation damage due to minority-carrier injection mainly results from recovery in minority-carrier diffusion length and decrease in recombination current. These mainly originate from the annihilation of the major defect centers H4 and E2 in the p-InP layer due to injection.

Carrier concentration effects on radiation damage in InP

Minority carrier diffusion length and carrier concentration studies have been made on room-temperature 1-MeV electron irradiated liquid-encapsulated Czochralski grown Zn-doped p-InP. The damage rate for the diffusion length and carrier removal rate due to irradiation have been found to strongly decrease with an increase in the carrier concentration in InP. These phenomena suggest that the induced defects interact with impurities in InP. A preliminary study on the annealing behavior has also been performed.

Radiation damage in InP single crystals and solar cells

This paper shows that InP solar cell is more radiation resistant than Si and GaAs solar cells. 60Co γ-ray irradiation damage in InP solar cells was examined. Changes in minority carrier diffusion length and carrier concentration in irradiated InP single crystals were also investigated by electron beam induced current and capacitance-voltage methods for solar cells. A high carrier concentration p-InP substrate has lower concentration damage. Thus, an InP solar cell with a higher carrier concentration substrate has superior radiation resistance. Experimental results for radiation damage in InP solar cells were in satisfactory agreement with theoretical values, calculated from changes in minority carrier diffusion length and carrier concentration due to irradiation. Numerical analysis suggests that an InP solar cell with a higher carrier concentration substrate and a shallower junction should be relatively more radiation resistant. Annealing behavior for radiation damage in InP was also examined.

Compensating aspects of implantation damage in InP

Electrical compensation inadvertently obtained with the introduction of dopant ions by implantation has been examined in InP. Intermediate mass sulfur and silicon ions implanted at 1 MeV are found to compensate InP at a removal rate ≈ 50 carriers per ion. Comparable rates to RT are again obtained on irradiating at 200 °C, indicating that the defect responsible for compensation differs from and is more stable than the general lattice disorder observed by backscattering. Its persistence also explains why elevated temperature implants are not active without further annealing. Annealing of the compensated layers at temperatures to 600 °C reveals two recovery stages and the presence of two distinct compensating defects as is the case in GaAs.

Damaged-induced isolation in n-type InP by light-ion implantation

A detailed study of the insulating properties of ion-implantation induced damage in InP has been carried out for H, He, B and Be implantation. For each ion, there was found to be an optimal implantation fluence for the formation of resistive layers. At this fluence, a maximum resistivity of 10 3 to 10 4Ω·cm was observed. Lower resistivities were observed for higher and lower implantation fluences. The primary anneal stage for the maximum resistivity layers was between 250 and 300°C. Anomalous results were observed for H implantation in that the resistivity observed depends on the test structure geometry. Measurements carried out by contacting the front and back of the damage layer gave resistivity values two orders of magnitude greater than those measured by contacting adjacent points on an epitaxial structure. For all other ions, the results obtained for the two geometries were in good agreement. It has been shown that a conductive layer produced by the proton bombardment of the underlying Fe-doped substrate gives rise to a low resistance shunt in the epitaxial study.

Ion implantation damage in InP

The disorder generated by 40 keV light (N +) and heavy (Bi +) ion irradiation of InP at 40 K and room temperature has been measured, using Rutherford backscattering channeling techniques, as a function of ion flux density and fluence. For the light ion irradiation the damage retained in the substrate is highly dependent upon irradiation temperature and upon flux density for room temperature irradiation. Such dependencies are much weaker for heavy ion irradiation. These results, together with the fluence dependence of disorder, are consistent with a mainly direct impact amorphisation, stable against annealing, process with heavy ion implantation and a mainly simpler defect generation, unstable against annealing, process with light ion implantation. Studies of disorder generation in both the In and P sublattices are also discussed.

Damage and reordering of ion-implanted layers of InP

Si ion-implantation damage in InP was studied by channeling measurements with 1-MeV4 He ions. 200-keV Si ions were implanted at fluences ranging from 1013 to 5×1014/cm2. A fluence of about 1014/cm2 was sufficient to produce an amorphous layer. Epitaxial annealing of amorphous layers takes place at temperatures below 250°C but leaves a high level of residual damage. Annealing at 450°C removes most of the lattice damage. Some annealing of lower fluence damage takes place at room temperature. Most lattice damage can be avoided by implanting with the substrate at an elevated temeperature (∼180°C).

Transmission electron microscope observations of damage in InP induced during handling

Damage observed in InP specimens following thinning and mounting in a specimen holder for transmission electron microscopy consisted of two kinds. In one case microcracks were observed in {110} cleavage planes. These contained edge dislocations with Burgers vectors of the type b= (a/2) 〈110〉. A second kind consisted of dislocation clusters which gave rise to slip and stacking-fault formation during examination in the microscope. The results suggest that extreme care is essential in handling this material during device processing.

Surface Damage in InP Induced during SiO2 Deposition by rf Sputtering

Surface Damage in InP Induced during SiO2 Deposition by rf Sputtering

Compensation from implantation damage in InP

Compensation arising from ion damage has been investigated in InP. It is found that ≳10 times the irradiation that produces resistive layers in GaAs is required to similarly compensate InP. The damage anneals in two stages indicating that two distinct defects contribute to the carrier removal process. Partial annealing at ∼400 °C rather than at 500 °C as in GaAs is suggested as a means of producing low-absorption highly resistive layers. From compensation considerations annealing to at least 550 °C will be required for dopant implantations if effective electrical utilization is to be achieved.