InGaAsP Planarized InGaAsP Semiconductor Lasers for Giga-bit Applications 1
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1.3µm SiO 2 (Benzocyclobutene, BCB) BCB SiO 2 SiO 2 laser die 500µm 300µm mount submound 34mA 1.31V 10.1Ω 76 3dB 1.9G 2
Abstract Ridge-type 1.3µm InGaAsP diode lasers with planar waveguide structure have beem successfully fabricated and mounted on silicon submounds. The laser diodes were fabricated by first etch a ridge structure for light guidance.typical ridge width is around 3µm. After ridge etching, a SiO2 thin film was sputtered onto the sample as surface passivation layer, fllowing by the coating of Benzocyclobutene (BCB) polymer for surface planarization.the unwanted BCB polymer was removed by dry etching process until the passivation oxide can be observed.before metallization, SiO 2 layers above the ridge were removed by wet etching technique. The fabrication was completed by evaporating contact metals to the samples. The finished samples were cleaved into laser dies with a dimension of 500µm 300µm.The dies were mounted onto a Si submound for DC and AC measurement.the threshold current of the planarized laser is 34mA.The threshold voltage and total resistance of the planar device are 1.31V and 10.1Ω.The quantum efficiency as large as 76 is obtained.the frequency response of the device is also measured.the 3dB bandwidth is about 1.9GHz 3
1 4 7 3-1 8 3-1.1 8 3-1.2 11 3-1.3 14 3-1.4 18 3-2 20 24 4-1 24 4-2 DC 24 4-3 27 4-4 AC 28 4-5 32 33 4
2-1 4 3-1 7 3-2 BCB 12 5
2-1 5 2-2 5 3-1 BCB 21 3-2 BCB 22 3-3 SEM 23 3-4 SEM 23 4-1 24 4-2 25 4-3 26 4-4 27 4-5 28 4-6 (To-can laser) 29 4-7 (our device) 29 4-8 4-6 (To-can laser) 30 4-9 4-7 (our device) 31 6
1.3µm optical fiber [1] 1.3µm [2, 3] lateral index guiding transverse active region cladding layer confinement 1.3µm 1.5µm 1.5µm ~ 2µm Flip-Chip submound Au/Sn Au 1
BCB Å Flip-Chip submound OEIC(Optoelectronic Integrate Circuit) waveguide alignment BPM-CAD BCB lift off mounting wire bounding 2
comb generator DC AC 3
2-1 (Correlation Function Method) fundamental mode 2-1 2-2 (x-direction) (y-direction) 2-1 layer Composition Thickness type Refractive index 0 InP Substrate 350µm n 3.148 1 InP Buffer 0.5µm n 3.19756 2 InAlAs 0.1µm n 3.19756 3 GRIN AlQ (AlT to 0.96) 0.15µm u 3.25 4 5QW, 6Barrier 5/8.5(nm) 3.4166 5 GRIN AlQ (0.96 to AlT) 0.15µm u 3.25 6 InAlAs 0.1µm u 3.206286 7 InP 0.17µm p 3.208 8 InGaAsP 25nm p 3.208 9 InP 0.18µm p 3.208 10 InGaAsP 50nm p 3.3 11 InGaAs 0.2µm p 3.4 4
BCB ridge BCB 2-1 ridge 2-2 5
FWHM 3.16µm 0.8µm n effect 3.22481 FWHM 3.16µm 0.8µm n effect 3.22482 BCB 1 BCB 1.6 6
3-1 : SiO2 BCB RIE SiO2 P N 7
3-1 3-1 3-1.1 (1) 10 5 8 (2) 10 5 8 (3) 10 5 8 (4) (3) (5) 1 120 30 (1) AZ-4210 6000 r.p.m 40 (2) 90 30 8
(3) I-line 42 Mask1 (4) AZ-400K = 1 4 53 (5) 100 15 (1) 1 : to etch InGaAs and InP H 2 O : HCl : HBr : H 2 O 2 = 50 : 10 : 10 : 1 H 2 O HCl HBr H 2 O 2 H 2 O HCl 15 HBr H 2 O/HCl/HBr 15 H 2 O 2 2: to etch InP and stop at InGaAsP A = H 2 O : HCl = 1 : 4 (10 : 40) B = CH 3 COOH : HBr = 1 : 1 (25 : 25) A B (2) 1 H 2 O 2 5 1 InGaAs InGaAsP InP 2 InP InGaAsP 2µm (3) 9
(4) (5) 30 InGaAsP etching stop layer MQW Mask 10
ridge 3µm 2µm 3-1.2 BCB BCB SiO2 SiO2 (1) 2500Å SiO2 250W 3m torr 11
BCB (1) BCB 3-2 ( ) 300 N2 on N2 off 150 70 20 28 43 58 118 3-2 BCB (min) (1) (RIE) (ECR) BCB SiO2 SF6 O2 6 5 (S.C.C.M) 10mtorr RIE 70W ECR 200W 12
SiO2 (1) BOE SiO2 NH4F H2O 70g 135 12 SiO2 SiO2 BCB BCB 7.5µm BCB 13
SiO2 contact layer 3-1.3 3.1-1 (1)~(5) (1) AZ-4210 6000rpm 40 (2) 90 30 (3) I-line 44 (4) AZ-400K 1 4 56 (1) HCl HCl 1 1 30 14
P (1) P Cr 420 Å Au Cr 500 Å 2500 Å Au/Sn submound Au/Sn contact (lift off) (1) (2) (3) (1) HCl HCl 1 1 30 N (1) n Au/Ge 500 Å 500 Å Au Au/Ge 15
(annealing) (1) 390 2 ridge BCB ` UV light 16
P p-metal 17
N p-metal n-metal 3.1-4 mounting (1) 500µm 300µm laser die (2) mount 3500Å Au/Sn submound 300 (1) mounting In wire bounding mounting LD submoun 18
wire bounding In SMA connector 19
3-2 BCB Flip-Chip SOG BCB BCB BCB SOG BCB BCB SOG SOG BCB 1.6 SOG BCB self-aligned [4] ρl R= A 20
BCB 2µm 2000 Å 3-1 Height(Å) ~ 2000Å Scan length(µm) 3-1 BCB BCB SF6[5] BCB SiO2 SiO2 BOE SiO2 SiO2 BCB SiO 2 CHF 3 21
SiO 2 BCB [6] sample Specific contact resistance BCB BCB SiO 2 Height(Å) 10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0 ~300Å 1 51 101 151 201 Scan length(µm) 3-2 BCB 22
BCB ridge 3-3 SEM ridge BCB 3-4 SEM 23
4-1 4-2 DC I-V 4-1 4-1 10.1 1.25 24
I-P 4-2 4-2 34mA (Differential Quantum Efficiency)[7] 76 25
Normalized Intensity Angle (degree) 4-3 FWHM(Full Width at Half Maximum)[8] 14 38 aspect ratio 1 3 26
4-3 comb generator RF Amplifier Bias T High Speed Measurement System RF Amplifier Comb generator Bias Tee laser diode lens detector DCA 100MHZ 9dBm Sine wave Signal generator oscilloscope 4-4 RF comb generator Bias T high speed detector( 2.5GHz) 27
4-4 AC Laser input pulse 4-5 4-6 241ps Bias T To-can 28
Laser ouput pulse (To-can) 1ns/div 4-6 (To-can laser) Laser output pulse(our device) 1ns/div 4-7 (our device) 29
4-7 4-8 To-can 4-6 696ps 527ps 4-7 4-8 4-9 4-10 2 0-2 Response(dB) -4-6 -8-10 -12-14 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Frequency(GHz) 4-8 4-6 (To-can) 30
2 0-2 Response(dB) -4-6 -8-10 -12-14 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Frequency(GHz) 4-9 4-7 (our device) 4-9 4-10 To-can 3dB 1.5GHz 1.9GHz 31
4-5 34mA current spreading cladding [9] buried heterostructure[10] active region cladding layer[11, 12] AC 241ps 696ps 527ps 3dB 1.5GHz 1.9GHz 2GHz 32
BCB mounting 34mA 1.31V 10.1Ω 76 3dB 1.9GHz mount submound mounting wire bounding wire 33
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