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[EN] Recently, two novel PET devices have been developed with open geometries, namely: breast and prostate-dedicated scanners. The breast-dedicated system comprises two detector rings of twelve modules with a field of view of 170 mm x 170 mm x 94 mm. Each module consists of a continuous trapezoidal LYSO crystal and a PSPMT. The system has the capability to vary the opening of the rings up to 60 mm in order to allow the insertion of a needle to perform a biopsy procedure. The prostate system has an open geometry consisting on two parallel plates separated 28 cm. One panel includes 18 detectors organized in a 6 x 3 matrix while the second one comprises 6 detectors organized in a 3 x 2 matrix. All detectors are formed by continuous LYSO crystals of 50 mm x 50 mm x15 mm, and a SiPM array of 12 x 12 individual photo-detectors. The system geometry is asymmetric maximizing the sensitivity of the system at the prostate location, located at about 2/3 in the abdomen-anus distance. The reconstructed images for PET scanners with open geometries present severe artifacts due to this peculiarity. These artifacts can be minimized using Time Of Flight information (TOF). In this work we present a TOF resolution study for open geometries. With this aim, the dedicated breast and prostate systems have been simulated using GATE (8.1 version) with different TOF resolutions in order to determine the image quality improvements that can be achieved with the existing TOF-dedicated electronics currently present in the market. The images have been reconstructed using the LMOS algorithm including TOF modeling in the calculation of the voxel-Line Of Response emission probabilities.

[EN] Recently, two novel PET devices have been developed with open geometries, namely: breast and prostate-dedicated scanners. The breast-dedicated system comprises two detector rings of twelve modules with a field of view of 170 mm x 170 mm x 94 mm. Each module consists of a continuous trapezoidal LYSO crystal and a PSPMT. The system has the capability to vary the opening of the rings up to 60 mm in order to allow the insertion of a needle to perform a biopsy procedure. The prostate system has an open geometry consisting on two parallel plates separated 28 cm. One panel includes 18 detectors organized in a 6 x 3 matrix while the second one comprises 6 detectors organized in a 3 x 2 matrix. All detectors are formed by continuous LYSO crystals of 50 mm x 50 mm x15 mm, and a SiPM array of 12 x 12 individual photo-detectors. The system geometry is asymmetric maximizing the sensitivity of the system at the prostate location, located at about 2/3 in the abdomen-anus distance. The reconstructed images for PET scanners with open geometries present severe artifacts due to this peculiarity. These artifacts can be minimized using Time Of Flight information (TOF). In this work we present a TOF resolution study for open geometries. With this aim, the dedicated breast and prostate systems have been simulated using GATE (8.1 version) with different TOF resolutions in order to determine the image quality improvements that can be achieved with the existing TOF-dedicated electronics currently present in the market. The images have been reconstructed using the LMOS algorithm including TOF modeling in the calculation of the voxel-Line Of Response emission probabilities.

[EN] Recently, two novel PET devices have been developed with open geometries, namely: breast and prostate-dedicated scanners. The breast-dedicated system comprises two detector rings of twelve modules with a field of view of 170 mm x 170 mm x 94 mm. Each module consists of a continuous trapezoidal LYSO crystal and a PSPMT. The system has the capability to vary the opening of the rings up to 60 mm in order to allow the insertion of a needle to perform a biopsy procedure. The prostate system has an open geometry consisting on two parallel plates separated 28 cm. One panel includes 18 detectors organized in a 6 x 3 matrix while the second one comprises 6 detectors organized in a 3 x 2 matrix. All detectors are formed by continuous LYSO crystals of 50 mm x 50 mm x15 mm, and a SiPM array of 12 x 12 individual photo-detectors. The system geometry is asymmetric maximizing the sensitivity of the system at the prostate location, located at about 2/3 in the abdomen-anus distance. The reconstructed images for PET scanners with open geometries present severe artifacts due to this peculiarity. These artifacts can be minimized using Time Of Flight information (TOF). In this work we present a TOF resolution study for open geometries. With this aim, the dedicated breast and prostate systems have been simulated using GATE (8.1 version) with different TOF resolutions in order to determine the image quality improvements that can be achieved with the existing TOF-dedicated electronics currently present in the market. The images have been reconstructed using the LMOS algorithm including TOF modeling in the calculation of the voxel-Line Of Response emission probabilities.

Ti/Pt metal layers are an integral part of the gate stack of many III-V field-effect transistors (FETs). These devices are known to be affected by H(sub 2) exposure. In this study, Auger Electron Spectroscopy (AES) measurements of Ti/Pt bilayers are correlated with electrical measurements of InAlAs/InGaAs/InP FETs fabricated with Ti/Pt/Au gates. The PET measurements show that H(sub 2) exposure shifts the device threshold voltage through the piezoelectric effect. AES reveals the formation of titanium hydride (TiH(sub x)) in Ti/Pt bilayers after identical H(sub 2) exposures. These results indicate that the volume expansion associated with TiH(sub x) formation causes compressive stress in Ti/Pt/Au gates, leading to the piezoelectric effect. After a I subsequent recovery anneal in N(sub 2), the FET measurements show that V(sub T) recovers. AES measurements confirm that the TiH(sub x) in hydrogenated Ti/Pt bilayers also decreases after further annealing in N(sub 2).

We have developed a methodology to diagnose the physical mechanisms limiting the manufacturing yield of millimeter-wave power InAlAs/InGaAs HEMTs on InP. A statistical analysis was carried out on DC figures of merit obtained from a large number of actual devices on an experimental wafer. Correlation studies and a Principal Component Analysis (PCA) of the results indicated that variations in Si delta-doping concentration introduced during MBE accounted for more than half of the manufacturing variance. Variations in the gate-source distance that is determined by the electron-beam alignment in the gate formation process were the second leading source of manufacturing variance.

At this time, GaAs PHEMTs exhibit higher power output than InP HEMTs at 60 and 94 GHz. InP HEMTs, however, feature power-added efficiency values that exceed GaAs PHEMTs by about 5 to 20 percentage points at 94 GHz. As a consequence, InP HEMTs remain a superior candidate for millimeter-wave power applications. The reason for the inferior output power of InP HEMTs lies in their relatively small on-state and off-state breakdown voltages. This paper reviews the state of the art of millimeter-wave power HEMT technology as well as recent advances in understanding of breakdown phenomena. It also discusses the prospects and challenges facing InP HEMTs in performance, reliability and low-cost manufacturing.

We have developed a methodology to diagnose the physical mechanisms limiting the manufacturing yield of millimeter-wave power InAlAs/InGaAs HEMTs on InP. A statistical analysis was carried out on DC figures of merit obtained from a large number of actual devices on an experimental wafer. Correlation studies and a Principal Component Analysis (PCA) of the results indicated that variations in Si delta-doping concentration introduced during MBE accounted for more than half of the manufacturing variance. Variations in the gate-source distance that is determined by the electron-beam alignment in the gate formation process were the second leading source of manufacturing variance.

At this time, GaAs PHEMTs exhibit higher power output than InP HEMTs at 60 and 94 GHz. InP HEMTs, however, feature power-added efficiency values that exceed GaAs PHEMTs by about 5 to 20 percentage points at 94 GHz. As a consequence, InP HEMTs remain a superior candidate for millimeter-wave power applications. The reason for the inferior output power of InP HEMTs lies in their relatively small on-state and off-state breakdown voltages. This paper reviews the state of the art of millimeter-wave power HEMT technology as well as recent advances in understanding of breakdown phenomena. It also discusses the prospects and challenges facing InP HEMTs in performance, reliability and low-cost manufacturing.

Optical anisotropy in mismatched In(x)Ga(1-x)As/InP and In(y)Al(1-y)As/InP heterostructures has been investigated by variable azimuthal angle ellipsometry and reflectance difference spectroscopy. The two approaches are shown to yield strongly correlated results. A comparison to high resolution x-ray diffraction, transmission electron microscopy, and atomic force microscopy studies indicates that large optical anisotropies are associated with surface roughening that results from three dimensional growth. Our findings demonstrate that fast and non-destructive measurements of optical anisotropy can provide important information about the growth mode and crystalline quality of strained epitaxial layers