Tatsunori Shirai

A planar InP/InGaAsP heterostructure avalanche photodiode

A new guard-ring structure for InP/InGaAsP heterostructure avalanche photodiodes (APDs) is presented. The guard ring consists of a linearly graded junction formed by beryllium ion implantation and two-step InP layers having different carrier concentrations (n-and n-layers grown on an InGaAsP layer). A planar InP/InGaAsP avalanche photodiode having this guard ring has a maximum avalanche gain of 110 at an initial photocurrent of 0.35 µA. The effectiveness of the guard ring is clearly discernible from the spot-scanned photoresponse of the diode.

Heterojunction Effect on Spectral and Frequency Responses in InP/InGaAsP/InGaAs APD

Influence of the valence band discontinuity on the spectral and frequency responses in InP/InGaAsP/InGaAs APDs has been reported. Quantum efficiency showed gradual increases in the wavelength range from 1.0 to 1.3 µm, where the absorption coefficients decrease with increasing wavelength. Frequency response deteriorations, which cannot be explained by usual deterioration mechanisms, were found at around 300 MHz. These two characteristics are due to holes piled up at the heterointerface which was confirmed experimentally. Recombination and thermionic emission of piled up holes cause the deterioration of quantum efficiency and frequency response, respectively. High speed APDs are realized by increasing the electric field of the heterointerface in InP/InGaAsP/InGaAs APDs.

Multiplication noise in planar InP/InGaAsP heterostructure avalanche photodiodes

Planar InP/InGaAsP avalanche photodiodes have been fabricated and multiplication noise is discussed. The effective hole to electron ionization rate ratio is found to be 1.9 from the wavelength dependence of multiplication noise.

Multiplication noise of InP avalanche photodiodes

An InP avalanche photodiode with a guard ring structure is fabricated. The maximum avalanche gain obtained is 210 at a primary photocurrent of 0.2 μA, and uniform photoresponse without local enlargement is obtained at an avalanche gain of 10. Multiplication noise characteristics are investigated, and the effective ionization rate ratio of holes to electrons is found to be 1.7–1.8.

High reliability planar InGaAs avalanche photodiodes

The reliability of planar buried-structure InGaAs APDs (avalanche photodiodes) for long-wavelength optical transmission systems was investigated. High-temperature aging tests were performed at 150 degrees C, 175 degrees C, and 200 degrees C, and two distinctive failure distributions (early failure and wear-out failure) were observed. The early failure is predicted to be caused by microplasma at the periphery of the guard ring junction, and the wear-out failure is related to the InP/SiN/sub x/ interface degradation by hot hole injection. The activation energy of the wear-out failure is estimated to be 1.15 eV, and the extrapolated median life at 50 degrees C exceeds 10/sup 8/ h. In the second step of the life testing, burn-in screening at 200 degrees C was shown to be effective in removing early failure and achieving long-term stability. 750000 h of device operation has been achieved without any failure at test temperatures of 125 degrees C and 150 degrees C, which indicates high reliability of the APDs.<<ETX>>

Improved responsivity at the L-band wavelength of a strain-compensated InGaAs multiple quantum well photodiode

The absorption layer of a strain-compensated InGaAs multiple quantum well (MQW) was shown to improve the responsivity at the L-band wavelength of a photodiode used in optical fiber communications. The MQW was examined to clarify the range of structural parameters, which are strain and thickness, with which a smooth surface morphology can be obtained. A photodiode with an absorption region of a strain-compensated MQW exhibiting a smooth surface morphology was fabricated, and it was proven to have a high crystalline quality with a low dark current. The MQW absorption region enabled the responsivity of the photodiode to exceed that of a lattice- matched InGaAs photodiode. Carrier transport vertical to the MQW layer was shown to be scarcely affected by the hole trapping caused by band discontinuity.