Université de Neuchâtel

Si-interdiffusion in heavily doped AlN-GaN-based quantum well intersubband photodetectors

Hofstetter, Daniel ; Di Francesco, Joab F. ; Martin, Denis ; Grandjean, Nicolas ; Kotsar, Yulia ; Monroy, Eva

In: Applied Physics Letters, 2011, vol. 98, no. 241101, p. 1-3

We demonstrate the effect of rapid thermal annealing on heavily Si-doped AlN/GaN quantum wells. After 1000 °C annealing during 5, 10, and 20 min, the dominant effect was interdiffusion of Si rather than intermixing between the Al and Ga atoms. Both their original value and the magnitude of the changes after annealing reveal that intersubband absorption and photovoltage are related to two...

Université de Neuchâtel

Intersubband spectroscopy probing higher order interminiband transitions in AlN-GaN-based superlattices

Hofstetter, Daniel ; Di Francesco, Joab F. ; Kandaswamy, Prem K. ; Monroy, Eva

In: Applied Physics Letters, 2011, vol. 98, no. 071104, p. 1-3

We investigate midinfrared intersubband photodetectors based on short-period AlN/GaN superlattices with different quantum well thicknesses. Band structure calculations, as well as optical transmission and photovoltage measurements, underline the importance of higher order interminiband transitions. In particular, it was found that optical transitions between the second and third minibands benefit...

Université de Neuchâtel

Latest developments in GaN-based quantum devices for infrared optoelectronics

Monroy, Eva ; Guillot, Fabien ; Leconte, Sylvain ; Nevou, Laurent ; Doyennette, Laeticia ; Tchernycheva, Maria ; Julien, François H. ; Baumann, Esther ; Giorgetta, Fabrizio R. ; Hofstetter, Daniel

In: Journal of Materials Science : Materials in Electronics, 2008, vol. 19, no. 8-9, p. 821-827

In this work, we summarize the latest progress in intersubband devices based on GaN/AlN nanostructures for operation in the near-infrared. We first discuss the growth and characterization of ultra-thin GaN/AlN quantum well and quantum dot superlattices by plasma-assisted molecular-beam epitaxy. Then, we present the performance of nitride-based infrared photodetectors and electro-optical...

Université de Neuchâtel

Intersubband Transition-Based Processes and Devices in AlN/GaN-Based Heterostructures

Hofstetter, Daniel ; Baumann, Esther ; Giorgetta, Fabrizio R. ; Théron, Ricardo ; Wu, Hong ; Schaff, William J. ; Dawlaty, Jahan ; George, Paul A. ; Eastman, Lester F. ; Rana, Farhan ; Kandaswamy, Prem K. ; Guillot, Fabien ; Monroy, Eva

In: Proceedings of the IEEE, 2010, vol. 98, no. 7, p. 1234-1248

We report on the physics, epitaxial growth, fabrication, and characterization of optoelectronic devices based on intersubband transitions in the AlN/GaN material system. While in 1999, only results of optical absorption experiments could be shown, photodetectors and modulators with operation frequencies beyond 10 GHz as well as optically pumped light emitters have been demonstrated recently. This...

Université de Neuchâtel

Performance Improvement of AlN–GaN-Based Intersubband Detectors by Using Quantum Dots

Hofstetter, Daniel ; Di Francesco, Joab F. ; Kandaswamy, Prem K. ; Das, Aparna ; Valdueza-Felip, Sirona ; Monroy, Eva

In: Photonics Technology Letters, IEEE, 2010, vol. 22, no. 15, p. 1087-1089

We report a strong performance improvement for 1.55-μm AIN-GaN-based intersubband photodetectors. Thanks to the use of quantum dots (QDs) instead of quantum wells (QWs), a factor of 60 could be gained in terms of maximum responsivity. In addition, this performance was achieved at a considerably higher temperature of 160 K instead of 80 K as typically seen for QWs. The responsivity of...

Université de Neuchâtel

Performance improvement of AlN/GaN-based intersubband detectors thanks to quantum dot active regions

Hofstetter, Daniel ; Di Francesco, Joab F. ; Baumann, Esther ; Giorgetta, Fabrizio R. ; Kandaswamy, Prem K. ; Das, Aparna ; Valdueza-Felip, Sirona ; Monroy, Eva

In: IR Focal Plane and Detector Development II (Proceedings of SPIE), 2010, vol. 7808, no. 78080A, p. 1-8

Since the operating mode of 1.55 µm AlN/GaN-based intersubband photodetectors is based on optical rectification, both the excited state lifetime and the lateral displacement of the carriers play an important role for performance optimization. We thus show here results of an improved detector generation based on a novel type of active region. Thanks to the use of quantum dots instead of quantum...

Université de Neuchâtel

High frequency measurements on an AlN/GaN-based intersubband detector at 1550 and 780 nm

Hofstetter, Daniel ; Baumann, Esther ; Giorgetta, Fabrizio R. ; Dawlaty, Jahan ; George, Paul A. ; Rana, Farhan ; Guillot, Fabien ; Monroy, Eva

In: Journal of Applied Physics, 2008, vol. 92, p. 231104 1-3

We report on high frequency measurements on an AlN/GaN-based intersubband detector using mode-locked solid state lasers. Our experiments involving laser wavelengths of 1550 and 780 nm demonstrate not only the capability of such devices to work both at the fundamental and at a higher order intersubband transition, but they also allowed us to push the high frequency detection limit up to a value...

Université de Neuchâtel

GaN/AlN short-period superlattices for intersubband optoelectronics: A systematic study of their epitaxial growth, design, and performance

Kandaswamy, Prem K. ; Guillot, Fabien ; Bellet-Amalric, Edith ; Monroy, Eva ; Nevou, Laurent ; Tchernycheva, Maria ; Michon, A. ; Julien, François H. ; Baumann, Esther ; Giorgetta, Fabrizio R. ; Hofstetter, Daniel ; Remmele, T. ; Albrecht, M. ; Birner, S. ; Dang, Le Si

In: Journal of Applied Physics, 2008, vol. 104, no. 9, p. 093501 1-8

We have studied the effect of growth and design parameters on the performance of Si-doped GaN/AlN multiquantum-well (MQW) structures for intersubband optoelectronics in the near infrared. The samples under study display infrared absorption in the 1.3–1.9 μm wavelength range, originating from the photoexcitation of electrons from the first to the second electronic level in the QWs. A...

Université de Neuchâtel

Monolithically integrated UV/IR-photodetectors based on an AlN/GaN-based superlattice grown on an AlGaN buffer layer

Hofstetter, Daniel ; Baumann, Esther ; Giorgetta, Fabrizio R. ; Théron, Ricardo ; Guillot, Fabien ; Monroy, Eva ; Golka, Sebastian ; Strasser, Gottfried

In: Physica status solidi (c), 2009, vol. 6, no. 2, p. S818-821

In this article, we demonstrate closely spaced, monolithically integrated photodetectors in two largely different wavelength ranges. The epitaxial structure of the devices was grown by plasma-assisted molecular-beam epitaxy on an AlN-on-sapphire template; it consists of a Si-doped AlGaN thin film, and a nearly strain compensated 40 period AlN/GaN superlattice with 1.0 nm thick GaN quantum wells...

Université de Neuchâtel

MBE growth of AlN/GaN-based photovoltaic intersubband photodetectors

Monroy, Eva ; Guillot, Fabien ; Baumann, Esther ; Giorgetta, Fabrizio R. ; Hofstetter, Daniel

In: Physica status solidi (a), 2008, vol. 205, no. 5, p. 1060-1063

We report on the molecular-beam epitaxial growth, fabrication and characterization of AlN/GaN photovoltaic quantum well infrared photodetectors operating at 1.55 µm. Devices display a spectrally-narrow photovoltaic response to p-polarized light in the near infrared at room temperature. We have analysed the effect of the growth temperature, quantum well thickness, and number of periods in the...