Mechanism And Characteristics Of S Passivation Of Silicon Surface

The main purpose of this thesis is to reduce the surface state of Si by S passivation, It is hoped that this technique can solve the problem of dangling bonds of the Si/SiC interface, and then expect to enhance the photoelectric properties of the device. Experiments were conducted using (NH4)2S and NH3.H2O mixed solution and (NH4)2S with the S powder then mixed with NH3.H2O to passivated Si (100) surface. Moreover, the Se powder was dissolved into (NH4)2S and the Si (100) surface was passivated by Se. The passivation effect of Si (100) was characterized by ?-?, C-V and XPS test. Considering the thermal stability of the samples under two kinds of passivation process and the reasons for the change of the minority carrier lifetime were studied. Finally, calculating and simulating the effects of the passivated surface by S and Se. The main conclusions of this paper are as follows:(1)Through the simulation of MS, it is found that the adsorption energy of S is lower than Se, which shows that the system is more stable after S adsorption.(2)XPS compared the passivated sillicon wafer by (NH4)2S solution and by (NH4)2S with S or Se powder.When the (NH4)2S solution was added into the S powder, the XPS spectra showed the peak of Si-S bond. was stronger, which indicated that more Si-S bonds were formed on the surface of Si. The samples of Se passivation only have Si-S peak, there was no Si-Se peak,indicating that the surface of the Si only formed a Si-S bond, not formed Si-Se bond.. Consistent with the simulation results.(3)The Schottky barrier height and the ideality factor of the contact between Ni, Ti and Cu before and after passivation were extracted by I-V method and C-V method, respectively. The experimental data show that the ideality factor of the passivated sample is more close to 1, and the barrier height is closer to the ideal value. And the addition of S powder has a better effect on the surface state than the pure (NH4)2S solution.(4)The (NH4)2S passivation samples and (NH4)2S with S powder passivation samples were respectively treated at 200?,300?,400? and 500? for 50s under Nitrogen atmosphere.The results of ?-? test showed that the passivation effect of the samples after (NH4)2S solution was degraded at 300?.and the passivation effect of the samples passivated by (NH4)2S with S powder was degraded at the temperature of 400 ?.(5) When the samples were irradiated by sunlight, the effective minority lifetime of S passivation samples increased exponentially with the increase of irradiation time, and decreased with the increase of storage time.