摘要:

The studies that have been carried out on reversible light induced changes in a‐Si:H and the advances made in the understanding of the Staebler‐Wronski effect are reviewed. Several reasons for the absence of quantitative agreeement between the results obtained using various experimental techniques, different a‐Si:H films and different a‐Si:H structures are discussed. The problems that exist in the direct correlation of the Staebler‐Wronski effect in intrinsic a‐Si:H with solar cell degradation are also reviewed and the use of Schottky barrier solar cell structures to overcome some of these problems is discussed.

ISSN:0094-243X    

DOI:10.1063/1.36490

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Highly‐resolved ESR spectra including29Si hyperfine structure were determined on undoped and P‐doped a‐Si:H using1H ENDOR technique. From the comparison of the spectra of undoped a‐Si:H between before and after the light soaking, spatial distribution of photo‐created dangling bonds is discussed in relation with the bond‐breaking model. Spin centers coupled with31P increase in P‐doped a‐Si:H after the light soaking.

ISSN:0094-243X    

DOI:10.1063/1.36529

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Picosecond photoinduced absorption (PA) decay time for doped samples decrease with illumination. These results indicate that the donor and/or acceptor levels increase with illumination for samples with doping levels greater than 10−4doping levels. The results are confirmed by hyperfine measurements of neutral donors. The change in doping efficiency due to illumination is explained in terms of the hydrogen motion model for all metastable changes.

ISSN:0094-243X    

DOI:10.1063/1.36530

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The electronic and optical properties of a‐Si,Ge:H,F alloys are investigated for the initial (as‐grown) state as well as after annealing, light soaking, and subsequent annealing. The optical absorption spectra were determined from optical transmission, the constant photocurrent technique and photothermal deflection spectroscopy. The photoconductivity and the temperature dependence of the dark conductivity were measured. A post‐deposition anneal was found to improve the measured properties for some of the alloys. The properties of the high gap, Eopt≳1.4 eV, and the low gap, Eopt<1.4 eV, alloys change differently with light soaking. For the high gap alloys, there is an increase in the subgap absorption, a decrease in the photoconductivity and the dark conductivity and an increase in the activation energy with light exposure. The low gap alloys show increasing subgap absorption with light soaking, however, the photoconductivity remains constant and the dark conductivity increases and its activation energy decreases.

ISSN:0094-243X    

DOI:10.1063/1.36504

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The influence of extended illumination on the photoconductivity in doped and undoped a‐Si:H films is studied. Stationary as well as transient measurements have been performed. It is confirmed that the main influence of extended illumination in undoped a‐Si:H is the generation of recombination centers. The effect of light soaking in doped material involves generation of states near the band edges.

ISSN:0094-243X    

DOI:10.1063/1.36515

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The kinetics of light‐induced defects in amorphous silicon p‐i‐n devices is investigated, according to the electron‐hole recombination mechanism but taking into account the effect of drift carriers transport. The beneficial effect of high internal electrical fields is confirmed and quantitatively estimated.

ISSN:0094-243X    

DOI:10.1063/1.36520

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The creation of metastable defects in magnetron sputtered a‐Si:H films by light soaking and keV electron irradiation has been investigated with two different methods. The change in the density of states (DOS) was directly determined using the space charge limited current (SCLC) technique on n+‐i‐n+structures with semitransparent top contacts. The electron beam induced current (EBIC) technique was used for a detailed study of the defect generation by keV electrons in Schottky diodes. We found that compared to light soaking keV electrons create about four orders of magnitude more defects if the same energy dose is deposited in the device or film. According to our results the defect generation is proportional to the electron dose Io⋅t. A model will be presented which is able to explain the direct generation of metastable defects by electron irradiation via an electronic excitation of the SiH‐complex.

ISSN:0094-243X    

DOI:10.1063/1.36521

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Thin films of intrinsic hydrogenated amorphous silicon (i‐a‐Si:H), as well as p‐i‐n a‐Si:H devices have been studied by electrochemical photocapacitance spectroscopy (EPS), in conjunction with current‐voltage, capacitance‐voltage, and impedance measurements. EPS spectra for both i‐material alone and p‐i‐n devices show the presence of two deep levels, about 0.9 eV and 1.2 eV below the conduction band mobility edge (ECB), corresponding, presumably, to the negatively charged (D−) and neutral (D°) Si‐dangling bond states, respectively. Light soaking induces substantial changes in the photocapacitance and impedance characteristics of the thin film a‐Si:H, while annealing restores these characteristics to their original state. The changes observed are consistent with a photoinduced process resulting in charge accumulation at the interfaces.

ISSN:0094-243X    

DOI:10.1063/1.36522

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The effect of the long‐time (up to 1000 hrs) repeated light exposure combined with annealing at different temperature (25∼200 °C) on the photoconductivity of an intrinsic amorphous silicon hydrogen alloy has been investigated. It was found that the degradation process was not entirely reversible if the annealing temperature was below the deposition temperature. The power indexes of the photoconductivity decay for some samples were larger than 1/3 which indicates that the metastable defects are generated not from direct electron‐hole pair recombination but from recombination through gap states. A new annealing behavior was observed, that is the photoconductivity of the degraded films didn’t show any sign of recovery when annealed below the degradation temperature (25 °C) for 800 hrs, but started to improve slowly when annealed at a temperature above 50 °C. The bond‐breaking model with a distribution of dangling bond distance is used to explain all these results.

ISSN:0094-243X    

DOI:10.1063/1.36523

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Photothermal deflection spectroscopy (PDS) and the constant photocurrent method (CPM) are used to monitor the changes in density of deep defects associated with the Staebler‐Wronski effect. These values are correlated with the electron spin resonance (ESR) signal, dc photoconductivity, and minority‐carrier &mgr;&tgr; values determined from bias‐dependent carrier collection efficiency studies. The density of deep defects determined by subgap absorption grows with light‐soaking timetfollowing the same functional form (t1/3) as the ESR signal. The initial and light‐induced defects have similar carrier recombination cross‐sections.

ISSN:0094-243X    

DOI:10.1063/1.36524

出版商:AIP    

年代:1987

数据来源: AIP