Effect of X-ray irradiation on threshold voltage of AlGaN/GaN HEMTs with p-GaN and MIS Gates

Commercially available AlGaN/GaN high-electron-mobility transistors(HEMTs)are beginning to enter the public scene froma range of suppliers.Based on previous studies,commercial GaN-based electronics are expected to be tolerant to different types of irradiation in space.To test this assumption,we compared the characteristic electrical curves obtained at different X-ray irradiation doses for GaN HEMT devices manufactured by Infineon and Transphorm.The p-GaN-based device was found to be more robust with a stable threshold voltage,whereas the threshold voltage of the device with ametal-insulator-semiconductor gatewas found to shift first in the negative and then the positive direction.This dynamic phenomenon is caused by the releasing and trapping effects of radiation-induced charges in the dielectric layer and at the interface of irradiated devices.As such,the p-GaNgate-based GaN HEMT provides a promising solution for use as an electric source in space.

Characterize and optimize the four-wave mixing in dual-interferometer coupled silicon microrings

By designing and fabricating a series of dual-interferometer coupled silicon microrings, the coupling condition of the pump, signal, and idler beams can be engineered independently and then we carried out both the continuous-wave and pulse pumped four-wave mixing experiments to verify the dependence of conversion efficiency on the coupling conditions of the four interacting beams, respectively. Under the continuous-wave pump, the four-wave mixing efficiency gets maximized when both the pump and signal/idler beams are closely operated at the critical coupling point, while for the pulse pump case, the efficiency can be enhanced greatly when the pump and converted idler beams are all overcoupled. These experiment results agree well with our theoretical calculations. Our design provides a platform for explicitly characterizing the four-wave mixing under different pumping conditions, and offers a method to optimize the four-wave mixing, which will facilitate the development of on-chip all-optical signal processing with a higher efficiency or reduced pump power.

RF characterization of InP double heterojunction bipolar transistors on a flexible substrate under bending conditions

This letter presents the fabrication of InP double heterojunction bipolar transistors(DHBTs)on a 3-inch flexible substrate with various thickness values of the benzocyclobutene(BCB)adhesive bonding layer,the corresponding thermal resistance of the InP DHBT on flexible substrate is also measured and calculated.InP DHBT on a flexible substrate with 100 nm BCB obtains cut-off frequency f_(T)=358 GHz and maximum oscillation frequency f_(MAX)=530 GHz.Moreover,the frequency performance of the InP DHBT on flexible substrates at different bending radii are compared.It is shown that the bending strain has little effect on the frequency characteristics(less than 8.5%),and these bending tests prove that InP DHBT has feasible flexibility.

CL-TWE Mach–Zehnder electro-optic modulator based on InP-MQW optical waveguides

In this Letter,we reported the preliminary results of an integrating periodically capacitive-loaded traveling wave electrode(CL-TWE)Mach–Zehnder modulator(MZM)based on InP-based multiple quantum well(MQW)optical waveguides.The device configuration mainly includes an optical Mach–Zehnder interferometer,a direct current electrode,two phase electrodes,and a CL-TWE consisting of a U electrode and an I electrode.The modulator was fabricated on a 3 in.InP epitaxial wafer by standard photolithography,inductively coupled plasma dry etching,wet etching,electroplating,etc.Measurement results show that the MZM exhibits a3 dB electro-optic bandwidth of about 31 GHz,a Vπof 3 V,and an extinction ratio of about 20 dB.

Bright photon-pair source based on a silicon dual-Mach-Zehnder microring

Single photons and photon pairs are typically generated by spontaneous parametric down conversion or quantum dots;however,spontaneous four-wave mixing(SFWM)in silicon microring resonators[1]is also an appealing source of entangled photons,offering a strong cavity-enhanced nonlinear interactions while maintaining features,such as compact,simple to fabricate,and allowing for thermal tuning.However,silicon ring-resonators usually suffer from a trade-off between providing a high pair generation rate(PGR)and high extraction efficiency.To achieve high PGR,devices are generally operated with the signal and idler photons in the undercoupling regime and pump photons at the critical coupling point,while high extraction rates require the converted photons to be overcoupled.Therefore,the optimal conditions for achieving maximal output photon pair flux are critical coupling for the pump photons and overcoupling for the converted photons[2,3].