Oxygen doping of c‐plane GaN by metalorganic chemical vapor deposition

Abstract

One of the most challenging tasks encountered in developing highly efficient electro‐optic (EO) devices is to find a material system that possesses all desirable properties such as large EO coefficients, good thermal and mechanical stability, and low optical loss. In order to meet this stringent requirement, we have developed a series of crosslinkable EO dendrimers using the standardized AJL8‐type chromophore as the center core and the furyl‐ and anthryl‐containing dendrons as the periphery. Upon adding a trismaleimide (TMI) dienophile, these dendrimers could be in‐situ crosslinked via the Diels–Alder cycloaddition and efficiently poled under a high electric field. Through this dynamic process, the spatially voided and π‐electron‐rich surrounding of the chromophore core changes into a dense and more aliphatic network, with the dipolar chromophore embedded and aligned inside. The resultant materials exhibit large EO coefficients (63–99 pm V–1 at 1.31 μm), excellent temporal stability (the original r33 values remain unchanged at 100 °C for more than 500 h), and blue‐shifted near‐IR absorption. With these combined desirable properties, a poled EOD2/TMI film could be processed through multiple lithographic and etching steps to fabricate a racetrack‐shaped micro‐ring resonator. By coupling this ring resonator with a side‐polished optical fiber, a novel broadband electric‐field sensor with high sensitivity of 100 mV m–1 at 550 MHz was successfully demonstrated.

The Role of Atmospheric Elements in the Wide Band-Gap Semiconductors

“…The first calculations based on the density functional theory showed [224], that oxygen is adsorbed more efficiently on the nitrogen side, whereby the crystal growth in the (000-1) direction produce a higher impurity concentration in the GaN layer. These results have been confirmed for both the MOCVD [225][226][227][228], as well as MBE [229] method. Higher oxygen concentration is also observed in crystal grown in non-polar and semipolar directions [230,231].…”

“…12). Special procedures aiming at reducing the oxygen-containing species adsorbed at the surface together with application of high density of primary current make it possible to reduce the detection limit by an order of magnitude as demonstrated in our laboratory [211,226,228,229,269] and Fig. 3.…”

Study of the stacking faults in a-plane GaN on r-plane sapphire grown by metal–organic chemical vapor deposition

“…As discussed earlier, PSFs formed at the initial coalescence stage of the GaN crystal islands and diminished gradually at two-dimensional (2D) growth process. Oxygen in sapphire substrate could diffuse into crystal film as donor doping atoms before coalescence finishing [17,18]. When growth changed into 2D mode, the diffusion process of oxygen atoms became difficult without the interval between the crystalline islands.…”

Fabrication and characterization of native non-polar GaN substrates

“…These regions have a different coloration and will affect the uniformity of the substrate. The coloration is believed to be associated with different incorporation rates of impurities during growth within the pitted region of the crystal [14]. The microstructure of these regions is described in the next section.…”