C. Ugolini

Excitation dynamics of the 1.54μm emission in Er doped GaN synthesized by metal organic chemical vapor deposition

The authors report on the excitation dynamics of the photoluminescence (PL) emission of Er doped GaN thin films synthesized by metal organic chemical vapor deposition. Using the frequency tripled output from a Ti:sapphire laser, the authors obtained PL spectra covering the ultraviolet (UV) to the infrared regions. In the UV, a dominant band edge emission at 3.23eV was observed at room temperature; this is redshifted by 0.19eV from the band edge emission of undoped GaN. An activation energy of 191meV was obtained from the thermal quenching of the integrated intensity of the 1.54μm emission line. This value coincides with the redshift of the band edge emission and is assigned to the ErGa-VN complex level.

1.54 μm emitters based on erbium doped InGaN p-i-n junctions

We present here on the growth, fabrication and electroluminescence (EL) characteristics of light emitting diodes (LEDs) based on Er-doped InGaN active layers. The p-i-n structures were grown using metal organic chemical vapor deposition and processed into 300×300 μm2 mesa devices. The LEDs exhibit strong emissions at 1.0 and 1.54 μm, due to Er intra-4f transitions, under forward bias conditions. The emitted EL intensity increases with applied input current without exhibiting saturation up to 70 mA. The integrated power over the near infrared emission, measured at room temperature from the top of a bare chip, is about 2 μW. The results represent a significant advance in the development of current injected, chip-scale emitters and waveguide amplifiers based on Er doped semiconductors.

Erbium-doped GaN optical amplifiers operating at 1.54 μm

Strip optical waveguides based on erbium (Er)-doped AlGaN/GaN:Er/AlGaN heterostructures have been fabricated and characterized in the optical communication wavelength window near 1.54 μm. The propagation loss of these waveguide amplifiers have been measured at 1.54 μm and found to be 3.5 cm−1. Moreover, the optical amplification properties of the waveguides were measured using a signal input at 1.54 μm and a broadband GaN light-emitting diode at 365 nm as pump source. A relative signal enhancement of ∼8 cm−1 was observed. The implications of such devices in photonic integrated circuits for optical communications are discussed.

Current-injected 1.54μm light emitting diodes based on erbium-doped GaN

Current-injected 1.54μm emitters have been fabricated by heterogeneously integrating metal organic chemical vapor deposition grown Er-doped GaN epilayers and 365nm nitride light emitting diodes. It was found that the 1.54μm emission intensity increases almost linearly with input forward current. The results represent a step toward demonstrating the feasibility for achieving electrically pumped optical amplifiers for optical communication that possess advantages of both semiconductor optical amplifiers and Er-doped fiber amplifiers.Current-injected 1.54μm emitters have been fabricated by heterogeneously integrating metal organic chemical vapor deposition grown Er-doped GaN epilayers and 365nm nitride light emitting diodes. It was found that the 1.54μm emission intensity increases almost linearly with input forward current. The results represent a step toward demonstrating the feasibility for achieving electrically pumped optical amplifiers for optical communication that possess advantages of both semiconductor optical amplifiers and Er-doped fiber amplifiers.

Optical enhancement of room temperature ferromagnetism in Er-doped GaN epilayers

We report on the enhancement of magnetic properties of Er-doped GaN epilayer structures, grown by metal-organic chemical vapor deposition, with illumination from a light emitting diode. Single and multiple Er-doped epilayers were grown with Er concentrations up to ∼1021 cm−3. All samples exhibited hysteresis behavior at room temperature as measured by an alternating gradient magnetometer. When the samples were illuminated at a wavelength of 371 nm, an increase in saturation magnetization was observed for each sample. The percentage increase for multiple layer samples ranged from 10%–25% indicating possible device applications.

Formation energy of optically active Er3+ centers in Er doped GaN

Erbium doped GaN (GaN:Er) and low In-content InxGa1−xN (x∼0.05) epilayers were synthesized by metal organic chemical deposition. The 1.54 μm PL emission intensity was monitored for GaN:Er epilayers grown at different growth temperatures and utilized to establish a value of 1.8 ± 0.2 eV for the formation energy (EF) of the optically active Er3+ centers in GaN. The optically active Er+ centers are presumably Er and nitrogen vacancy (Er-VN) complexes. The experimentally measured value of the EF of the optically active Er3+ centers is about 0.98 eV larger than the calculated formation energy of Er ions at Ga sites; however, it is 1.1–2.2 eV lower than the formation energy of VN in GaN. Due to the large EF values, relatively high growth temperatures are required to improve the 1.54 μm emission efficiency in GaN:Er.

Photoluminescence properties of erbium doped InGaN epilayers

We report on the photoluminescence properties of erbium (Er) doped InxGa1−xNa epilayers synthesized by metal organic chemical vapor deposition. The crystalline quality and surface morphology of Er doped In0.05Ga0.95N were nearly identical to those of Er doped GaN. The photoluminescence intensity of the 1.54 μm emission in Er doped In0.05Ga0.95N was an order of magnitude lower than in Er doped GaN and decreased with the increase of the In content. The reduction in 1.54 μm emission intensity was accompanied by enhanced emission intensities of deep level impurity transition lines.