Jeremy Burroughes

1.3- mu m P-i-N photodetector using GaAs with As precipitates (GaAs:As)

The fabrication of a GaAs detector which operates in the 1.3- to 1.5- mu m optical range is reported. The detector is a P-i-N photodiode with an intrinsic layer composed of undoped GaAs which was grown at 225 degrees C and subsequently annealed at 600 degrees C. This growth process has been demonstrated to produce a high density of As precipitates in the low-temperature grown region, which the authors show to exhibit absorption through internal photoemission. The internal Schottky barrier height of the As precipitates is found to be 0.7 eV, leading to reasonable room-temperature responsivity out to around 1.7 mu m.<<ETX>>

H-MESFET compatible GaAs/AlGaAs MSM photodetector

GaAs/Al/sub 0.3/Ga/sub 0.7/As short wavelength metal-semiconductor-metal photodetectors (MSM-PDs), compatible with GaAs heterostructure MESFET technologies have been fabricated. Detector bandwidths greater than 3.5 GHz were observed for lambda =800-850 nm. Due to the GaAs/AlGaAs heterojunction, low-frequency gain which is observed in GaAs MSM-PDs was minimized. The internal quantum efficiency was close to 100% and the dark currents were less than 1 nA for large-area detectors.<<ETX>>

1.3 mu m InGaAs MSM photodetector with abrupt InGaAs/AlInAs interface

The authors have fabricated long-wavelength abrupt-junction InGaAs/AlInAs metal-semiconductor-metal photodetectors that are potentially compatible with AlInAs/InGaAs H-MESFETs. The detectors have nanoampere dark currents and low capacitance. The responsivity at 10 MHz is 0.32 A/W, corresponding to at least 90% internal collection efficiency. The device performance limitations due to charge storage at the InGaAs/AlInAs interface are discussed, and it is shown that despite charge pile up, high data rates (>3 GHz) have been achieved at low bias voltages, provided the incident intensity is low.<<ETX>>

Doping-induced bandwidth enhancement in metal-semiconductor-metal photodetectors

A novel technique is demonstrated for enhancing metal-semiconductor-metal photodetector bandwidths without reducing responsivity. The authors have observed bandwidth increases of up to 10 GHz from control to enhanced photodetectors which corresponds to about 70% enhancement. This technique involves modifying the internal electric field structure, by introducing a buried n-type doped layer that is completely depleted, to reduce the relatively long hole transit time.<<ETX>>

Lateral Ga/sub 0.47/In/sub 0.53/As and GaAs p-i-n photodetectors by self-aligned diffusion

Contact-self-aligned diffusion and compositional mixing has been utilized in the fabrication of lateral p-i-n photodetectors in Ga/sub 0.47/In/sub 0.53/As and GaAs for 1.3- and 0.85- mu m wavelength operation. The p-type contact and diffusion utilizes W(Zn) metallurgy and the n-type contact and diffusion utilizes MoGe/sub 2/ metallurgy. Bandwidths exceeding 7.5 and 18.0 GHz, respectively, have been obtained using these structures with bias voltages of approximately=5 V. The performance, ease of fabrication, and process compatibility make these devices suitable for integration in digital circuits employing field-effect transistors.<<ETX>>

Lateral p-i-n photodetectors with 18 GHz bandwidth at 1.3 mu m wavelength and small bias voltages

Simultaneous n-type and p-type diffusion, compositional mixing, and formation of ohmic contacts have been used in the fabrication of lateral p-i-n photodetectors for short (0.85 mu m) and long (1.3 mu m and 1.5 mu m) wavelengths. Zinc-doped tungsten and MoGe/sub 2/ are used for the p-type and n-type contacts, doping, and compositional mixing using rapid thermal processing at approximately=750 degrees C. With structures utilizing GaAs and Ga/sub 0.47/In/sub 0.53/As active regions, 3 dB bandwidths exceeding 7.5 GHz and 18.0 GHz, respectively, have been achieved at bias voltages of approximately=5 V. The corresponding dark currents are sub-100 pA and sub-10 nA and the devices exhibit a large dynamic range, near-ideal responsivity, and a high sensitivity. The performance, ease of fabrication, and process compatibility make these devices suitable for integration in digital circuits using FET.<<ETX>>

GaAs see the light (photodetectors)

Summary form only given. Reported are p-i-n photodetectors using GaAs with As precipitates (GaAs:As) that detect 1.3- mu m light with reasonable efficiency. Since high-performance GaAs electronic circuits can be epitaxially grown on GaAs:As, this work may open the way for an all-GaAs 1.3- mu m optical receiver chip. In the GaAs p-i-n devices, the i layer was a 1- mu m-thick layer of GaAs:As. MSM structures with GaAs:As as the optically active material were also made. >