VÉZIAN , Stéphane

International audience

The polarization of the light emitted by an ultraviolet light-emitting diode (LED) has a direct impact on the device performance: a transverse electric polarization of the emission is preferred for extraction from the surface of the diode grown along the c axis. While this is the case for most UV LEDs grown on AlN, this state of events could be...

Due to its large piezoelectric and spontaneous polarization coefficients combined with the possibility of being grown lattice-matched with GaN, wide bandgap ScAlN is becoming a promising material in III-nitride semiconductor technology. In this work, and for the first time, ScAlN growth has been performed by molecular beam epitaxy with ammonia...

We build new material descriptors to predict the band gap and the work function of 2D materials by tree-based machine-learning models. The descriptor's construction is based on vectorizing property matrices and on empirical property function, leading to mixing features that require low-resource computations. Combined with database-based...

Thermal properties have an outsized impact on efficiency and sensitivity of devices with nanoscale structures, such as in integrated electronic circuits. A number of thermal conductivity measurements for semiconductor nanostructures exist, but are hindered by the diffraction limit of light, the need for transducer layers, the slow-scan rate of...

Securing optical information to avoid counterfeiting and manipulation by unauthorized persons and agencies requires innovation and enhancement of security beyond basic intensity encryption. In this paper, we present a new method for polarization-dependent optical encryption that relies on extremely high resolution near-field phase encoding at...

Intensity and polarization are two fundamental components of light. Independently control of them is of tremendous interest in many applications. In this paper, we propose a general vectorial encryption method, which enables arbitrary far-field light distribution with the local polarization, including orientations and ellipticities, decoupling...

We fabricated GaN-based hollow nanowires standing upright on a sapphire substrate by the sublimation method and found that they exhibit laser oscillation at room temperature. These very long, hollow, nanosized structures cannot be fabricated by other means. Furthermore, we determined the condition under which the fundamental mode is azimuthally...

A porous InGaN/GaN blue light-emitting diode is demonstrated using selective area sublimation. Transmission electron microscopy reveals that the structure is porous down to the Si substrate; however, the porosity is higher in the GaN buffer, while smaller pores are observed in the active region. This change of porosity between the active region...

International audience

In this paper, we report on the fabrication of a normally-off Al(Ga)N/GaN high electron mobility transistor with selective area sublimation under vacuum of the p type doped GaN cap layer. This soft method makes it possible to avoid damages otherwise induced by post processing with reactive ion etching techniques. The GaN evaporation selectivity...