Takao Ninomiya

25 GHz-spacing wavelength monitor integrated DFB laser module using standard 14-pin butterfly package

A 25 GHz-spacing wavelength monitor integrated DFB laser module has been successfully fabricated using standard 14-pin butterfly package. By employing separate temperature control for the LD and etalon, excellent wavelength locking performance (wavelength drift < /spl plusmn/0.2 pm) has been achieved using a simple analogue circuit.

Experimental Study of Beam Steering in 980-nm InGaP Cladding Lasers

The beam steering phenomenon was directly observed by means of backplane electroluminescence in 980 nm InGaP cladding power lasers. The electroluminescence of the lasers which showed lateral beam steering had a periodic pattern along the active region, which was assumed to be due to spatial hole burning. The period of this pattern was roughly estimated using the effective refractive index method. A laser satisfying the cut-off condition for higher lateral modes did not exhibit a periodic pattern of electroluminescence.

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.

Emitter Material Comparison between InGaP and InGaAsP in GaAs-Based Heterojunction Bipolar Transistors

In0.49Ga0.51P ( Eg=1.87 eV)/GaAs and In0.38Ga0.62As0.22P0.78 ( Eg=1.77 eV)/GaAs Npn heterojunction bipolar transistors (HBTs) were fabricated. In devices with 110 µm×110 µm emitter areas, the curtent gains of both devices were the same value of 14 at a collector current density of 700 A/cm2. By contrast, the turn-on voltage of InGaAsP/GaAs HBTs was 0.01 V smaller than that of InGaP/GaAs HBTs, which indicated that the conduction band discontinuity of the InGaP/InGaAsP heterojunction was much smaller than the valence band discontinuity.

Compositionally graded C-doped In/sub 1-x/Ga/sub x/As base in InP/InGaAs D-HBTs grown by MOCVD with low base sheet resistance and high current gain

MOCVD-grown carbon (C)-doped InGaAs layers using CBr/sub 4/ as a C source were investigated with the van der Pauw method and PL measurement. A hole concentration of as high as 7/spl times/10/sup 19/ cm/sup -3/ was obtained at a growth temperature of 385/spl deg/C. However, PL intensity of the C-InGaAs depends on the growth temperature, and was weaker than that of Mg- or Zn-doped InGaAs at a range of over 1/spl times/10/sup 19/ cm/sup -3/. Furthermore, DC measurement of D-HBTs revealed that there existed a strict tradeoff between the current gain and base sheet resistance of C-InGaAs uniform-base D-HBTs. To break through the tradeoff, we have fabricated D-HBTs with 150-nm-thick strain-compensated graded-In/sub 1-x/Ga/sub x/As-base (X=0.42/spl rArr/0.53). As a result, a current gain of 55 with a base sheet resistance of 480 /spl Omega///spl square/ was achieved.

Graded-GaAs/sub 1-x/P/sub x/ base in heterojunction bipolar transistors with InGaP emitters

We have fabricated the graded-GaAsP base HBTs with InGaP emitters for the first time. It was confirmed that heavy carbon-doping into GaAsP, as well as GaAs, could be realized by using MOCVD. The measured current gain was as high as over 100 at a collector current density (J/sub c/) of 3/spl times/10/sup 4/ A/cm/sup 2/. Furthermore, compared with the uniform-GaAs base HBTs, current-gain enhancement due to the built-in field in the base of the graded-base HBTs was also confirmed in a range of J/sub c/=1/spl times/10/sup 2/ A/cm/sup 2/ to 3/spl times/10/sup 4/ A/cm/sup 2/.

Very Weak Dependence on Temperature of 980-nm InGaAs/InGaAsP/InGaP Lasers

The effects of mirror loss on the characteristic temperature T0 were studied for 980-nm strained-layer InGaAs single-quantum-well graded-refractive-index separate-conlinement-heterostructure lasers with InGaP cladding layers. It was found that the lasers exhibited a very high T0 of over 300 K and strong dependence on temperature with change in the mirror loss. Assuming the logarithmic current ( J) -gain ( G) relation G=G0 ln(J/J 0), these phenomena could be interpreted using the behavior of the temperature dependence of G0.