Takeharu Yamaguchi

Magnesium-doped InGaAs using (C2H5C5H4)2Mg: application to InP-based HBTs

Heavily magnesium-doped p-type-InGaAs layers on InP(100) substrates were successfully grown, for the first time, by low-pressure metalorganic chemical vapor deposition (MOCVD) using bis-ethylcyclopentadienyl-magnesium, (C 2 H 5 C s H 4 ) 2 Mg (EtCp 2 Mg), as organometallic precursor for the Mg. It was experimentally verified that the room-temperature hole concentration of Mg into InGaAs increased with increase of the V/III ratio and decrease of the growth temperature. A maximum hole concentration of over 4x10 19 cm -3 was obtained. The diffusion coefficient of Mg in InGaAs was experimentally derived to be 10 -12 cm 2 /s at 800°C, which was comparable to that of Be. Finally, InP/InGaAs heterojunction bipolar transistors (HBTs) with Mg-doped bases were fabricated successfully. Measured maximum current gain was about 320 with a 90 nm thick base and a sheet resistance of the base layer of 1.28 kΩ/sq.

GaInAsP/InP attenuator integrated waveguide photodetector (AIPD) based on the Franz-Keldysh effect

A waveguide photodetector monolithically integrated with an optical attenuator based on the Franz-Keldysh effect at the input section is proposed. The intrinsic sensitivity of the device without attenuation is 0.25 A/W. The effective sensitivity is reduced by applying the reverse bias at the attenuator section. The largest variable sensitivity range of 11 dB is realized at the reverse bias of 32 V.