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EFFECT OF SPUTTERING TlMEAND RF POWER ON THE CURRENT-VOLTAGE CHARACTERISTICSOF AMORPHOUS (UNDO PED) SILICON FILMSDEPOSITED ON CRYSTALLINE SILICON BY RF SPUITERTNG.MANUEL J. CORO NADO AND A. SMGHLaboratorio de Semiconductores, Universidad de Oriente, Departameuto de Fisica,Apartado 287, Cumana , 6101, Sucre, Venezuela.

ABSTRACTThe samples A, B, C. D. E, and F were fabricated, depositing films of amorphous silicon(a-Si) by RF Sputtering on p-type crystalline silicon (c-Si) substrates, besides the controlsample M / S which was free of a-Si Ohmic contacts to c-Si substrates were obtained bysputter deposition of Al, followed by I5 min annealing at 500' C Top Ni contacts wereprepared by thermal deposition The room temperatu re current-v oltage (I-V) characteristics ofall the samples were measured in the range from -1OV o +1OV The experimental data was

described by a relation of the form J a Vm with 0.5

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with the m values listed in Table I. The J-V data for m>>2, was fitted to the theoreticalrelation [6]

TABLE ISummary of m values obtained by fitting the experimental I-V data to th e theoretical Eq (1)

and values of the barrier heights I $ ~ ,xtracted %om the Eq (2)RANGE m RANGE m RANGE m (v)EVICE OF OF OFVOLTAGE VOLTAGE VOLTAGEM/S 1 5 -1 t o - 1 0 V 3.3 0 50

A 3 9 - 1 t 0 - 2 8 V 2 7 -3 t0 -1O V 4 . 0 0 7 2B 1 9 - 1 t 0- 2 8 V 3 0 - 3t 0 -1 0 V 5 7 0 7 0C O V t o - 1 V 1 9 - l t o - 1 0 V 3 0 0.48E 1.5 -1 to -lO V 2.7 0.74M/S 1.3 1.3 to3.5 V 6.6 3.5 to 1OV 4.0 0.60A 1 4 1 .3 to 3.5 V 2 4 3 5 t o 1 0 V 3 . 3 0 7 3B 1.4 1 . 3 t o 3 5 V 35. 3 5 t o l O V 6 0 0 8 7C O V t o l V 0 6 1 3 t o 3 5 V 1 6 3 5 t 0 1 0 V 2 .0 0.58

D 0 . 9 1 3 t o 3 5 V 1 7 3 5 t o 1 0 V 2 0 0 6 2E 0.5 1.3 to 3.5 V 3.4 3 .5 to 1OV 1 9 0.74F 1.9 1.3 to3 .5 V 1.5 3.5 to 1OV 26 0.67

D 2 0 - 1 to-2 8 V 3 8 -3 to - lOV 3.3 04 8F 2.3 -1 to-2.8 V 2.2 -3 to -1 0V 3.3 0.54

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717This abov e analysis provide d the values of the ze ro bias bar.ier heigh ts $Bo. given in Table I.

DISCUSSIONThe values of forward to reverse current ratio at 5 V for the devices A, B, C and D

devices were 7, 2, 1 046 and 870, respectively, which indicated that the rectification ratioimproved with the increase in the deposition time of a-Si film upto 1 hr and worsened athigher sputter times. From T able 1, it can be seen that for forward bias voltages in the range -1 V