| 1. |
|
|
| 2. |
|
|
| 3. |
- Wang, Q., et al.
(författare)
-
Wide-aperture GaAs/AlGaAs multiple quantum well electro-optic modulators
- 2002
-
Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 4947, s. 59-67
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We present design and fabrication methods for surface normal monolithic amplitude modulators with an aperture up to 14 × 14 mm2, a contrast ratio of 6:1 and for low driving voltages (=8 V). The modulators consist of undoped GaAs/AlGaAs quantum wells embedded in a Fabry-Perot (FP) resonance cavity grown by MOVPE. To improve the device performance the FP cavity, the period and thickness of the quantum well and doping concentration were optimised. Also, the dimension of the modulator were varied from 0.5 × 0.5 to 14 × 14 mm2. The results show that the yield of the modulators increases significantly when decreasing the size of the modulators. To remedy the low yield issue for wide aperture modulator, a pixelated approach was used to divide the mono pixel in a monolithic modulator into several pixels, for example from 4 to 48. The modulation speed of the modulators with different dimensions was characterised by electro-optic (EO) response measurements. The temporal optical response of the large modulators was satisfactory up to the order of MHz modulation frequency where the RC constant limited the performance. A few of the modulators with wide apertures are to be assembled into an optical link system for free-space communication.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Höglund, Linda, 1974-, et al.
(författare)
-
Quantum dots-in-a-well infrared photodetectors for long wavelength infrared detection
- 2006
-
Ingår i: Proceedings of SPIE. - Bellingham, Wash. : SPIE - International Society for Optical Engineering. - 9780819464996 ; 6401, s. 1-640109
-
Konferensbidrag (refereegranskat)abstract
- We report on a quantum dots-in-a-well infrared photodetector (DWELL QDIP) grown by metal organic vapor phase epitaxy. The DWELL QDIP consisted of ten stacked InAs/In0.5Ga0.85As/GaAs QD layers embedded between n-doped contact layers. The density of the QDs was about 9 × 10 10 cm-2 per QD layer. The energy level structure of the DWELL was revealed by optical measurements of interband transitions, and from a comparison with this energy level scheme the origin of the photocurrent peaks could be identified. The main intersubband transition contributing to the photocurrent was associated with the quantum dot ground state to the quantum well excited state transition. The performance of the DWELL QDIPs was evaluated regarding responsivity and dark current for temperatures between 15 K and 77 K. The photocurrent spectrum was dominated by a LWIR peak, with a peak wavelength at 8.4 μm and a full width at half maximum (FWHM) of 1.1 μm. At an operating temperature of 65 K, the peak responsivity was 30 mA/W at an applied bias of 4 V and the dark current was 1.2×10-5 A/cm2. Wavelength tuning from 8.4 μm to 9.5 μm was demonstrated, by reversing the bias of the detector.
|
|
| 8. |
- Linnarsson, Margareta K., et al.
(författare)
-
Influence of layer thickness and primary ion on profile broadening during sputtering of Al0.5Ga0.5As/GaAs structures
- 1994
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 85:1-4, s. 395-398
-
Tidskriftsartikel (refereegranskat)abstract
- Broadening of secondary ion mass spectrometry depth profiles for Al in Al0.5Ga0.5As/GaAs structures, where the layer thicknesses vary from two monolayers to 1000 Å, is investigated. The experiments were performed in the net primary energy range 1.8–13.2 keV with 40Ar+ ions and 84Kr+ ions. The broadening is mainly determined by ballistic mixing, and no dependence on the Al0.5Ga0.5As layer thickness is revealed. Good agreement is found with a semi-empirical mixing model published recently by Zalm and Vriezema and [Nucl. Instr. and Meth. B 67 (1992) 467] although a small contribution from surface roughness occurs. The surface roughness develops initially but saturates already after the first Al0.5Ga0.5As layer.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
