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High-Power AI-Free Buried InGaAsP/GaAs (A =0.8 ,urn) Laser Diodes

D.Z.Garbuzov, N.Y.Antonishkis, N.D.Il’inskaya, S.N.Zhigulin N.I.Katsavets, A.V.Kochergin, V.Z.Pyataev, M.V.Fuksman.

A.F.Ioffe Physico-Technical Institute, St.Petersburg, Russia

Al-free InGaAsPIGaAs SCH SQW (h=0.8 pm) single-mode buried laser diodes having parameters comparable with the best achievements for AlGaAs/GaP.s diodes have been fabricated for the first time.

Previous publication [1,21 demonstrated the principal advantages of Al-free InGaAsP/GaAs system as a material for A= 0,8pm laser diode design in comparison with traditional AlGaAs/GaAs structures. The absence of easily oxidized AlGaAs-compounds make it possible to apply the widely used for InGaAsP/PnP infrared diodes method of chemical mesa-etching and regrowth for fabrication of 0,8 pm buried InGaAsP/GaAs diodes under study. A schematic of the laser diode is shown in Fig.1. Four-layed p-n-p-n blocking In Ga P structure was formed in regrowth process. Several tricks were used to diminish mesa-side-wall current leakage [31. The results considered below were obtained for laser diodes with cavity length of about 0.8 nlm having high reflective coating on the rear mirror facet which were bonded with indium p-side down onto the copper heatsink. CW light-current characteristic and low current part of pulse(z=100 ns) light-current characteristic for two diodes fabricated from a wafer with W=7pm are shown in Fig.2. The far field pattern in the p-n junction plane representing the combination of zero- and first transverse mode (Fig.3) was stable through whole output power range studied (up to 0.5 W). The maximum light output power was about 0,5W in CW operation and 1,2W in pulse regime. Single mode, single frequency operation was obtained for laser diodes with W=3,8 pm (Fig.3). The non-zero mode contribution was less than 10% up to the output power of 150mW. maximum output power was about of 300 mW.

Low near mirror facet losses for lasing mode are the main reason of high power density output operation for InGaAsP/GaAs diodes. The photoluminescence technique was applied to determinate of local mirror facet temperature rise 141. The results of AT versus driving current arid output power measurement for one of the laser diode with W=7pm are shown .in Fig.4 by solid curve. The measured AT values correspond to the total mirror facet overheating which is the sum of active region bulk (AT 1 and mirror

facet temperature rises (AT 1 . The dashed curve shows result of our

extrapolation f o r ATb with value of diode thermal resistance being

determined under assumption ATb=AT in the current range below the

threshold. As one can see in Fig.40 optical component of mirror facet overheating (AT ) is less then 10 C even at P =0.37 W, that is o:ie

order of magnitude less than for AlGaAs/GaAs laser diodes under the sa:ne optical power density 151.

0.49 0.51

b

opt

opt opt

1. D.Z.Garbuzov, et al. 12th IEEE International Semiconductor Lasx-

2 . D.Z.Garbuzov et al. IEEE QE-27, p.1531 1991. 3. D.Z. Garbuzov, I .E. Berishev, Yu. V. 11’ in, N.D. 11’ inskaya,

4. D.Z.Garbuzov, et al.,CLEO-91, Conf. Digest, v.10, p.142, 1991. 5. H.Bruggar and P.W.Epperlein, Appl.Phys.Let-t. 56, p.1049, 1990.

Conference, Davos, Switzerland, 1990 p.236.

A.V.Ovchinnikov, 1.S.Tarasov J.Appl;.Phys. to be published.

224

I InGaAsP/GaAs SCH SQW 1 = 0.8 pm

40

30

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1 In0.49 G%.Sl P:Te 1nGaP:Zn , 1.9

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E 1.7

1.54 --

1.4 I- I I 200 A - I

N I I’ I

w = 7 p m InGaP p-q mi InGaP

I n-GaAs \ Fig.1 The structure band-diagram and laser diode scheme.

InGaAsP/CaAs buried W = 7prn 7-A05 I ( I )

)f up lo 1.2 w (a) 500 I-

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0.2 0.4 0.6 0.8 (A)

Fig.2(a) Low-current part of pulse and CW light-current characteristics for diodes with W=7 pm. (b) Far field patterns in the p-n junction plane for one of the diode.

,, InGaAsP/GaAs SCH SQW LPE w = 3.8 pm upto1 w/

/ / 12-A9840

100 200 300 400 1 (mA)

Fig.3 The same as in Fig.2, but for a diode with W=3.8 pm. In addition several lasing spectra are shown.

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Fig.4 Solid curve is the total mirror facet overheating for diode with W=7pm. Dashed curve represents the extrapolation f o r bulk active region temperature rise ATb=R (I*V- Pop,) , where R - diode thermal resistance, I*V - electric power, P - diode optical output power. opt

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