Deep level transient spectroscopy DLTS

Experimentally, local vibrational modes associated witli a defect or impurity may appear in infra-red absorjrtion or Raman spectra. The defect centre may also give rise to new photoluminescence bands and otlier experimentally observable signature. Some defect-related energy levels may be visible by deep-level transient spectroscopy (DLTS) [23]. 

Figure 1 shows a deep level transient spectroscopy (DLTS) (Lang, 1974) spectrum from a Au-diffused, n-type Si sample before and after hydrogenation of 300°C for 2h (Pearton and Tavendale, 1982a). The well-known Au acceptor level (Ec - 0.54 eV) was passivated to depths > 10 pm under these conditions and was only partially regenerated by a subsequent... 

Bhattacharya, R. N. Balcioglu, A. Ramanathan, K. 2001. Deep-level transient spectroscopy (DLTS) of CdS/CuIni xGaxSe2-based solar cells prepared from electroplated and auto-plated precursors, and by physical vapor deposition. Thin Solid Films 384 65-68. 

The first technique is successfully used not only in the stndy of chemical reactions bnt also in electronic reaction kinetics in solids. It is necessary to note here the recently developed technique of deep-level transient spectroscopy (DLTS). 

Because of the previously mentioned reviews (Sah et al., 1970 Milnes, 1973 Grimmeiss, 1974, 1977, 1980 Sah, 1976 Miller et al., 1977 Lang, 1979 Martin, 1980), this section will be brief and mainly discuss techniques not previously reviewed. However, in view of the widespread use of deep level transient spectroscopy (DLTS) and the number of variations it has inspired, it is appropriate to describe briefly the technique. The reader is referred to the original article by Lang (1974b) and the review papers by Miller et al. (1977) and Lang (1979) for details. 

Fig. 4. Energy below the conduction band of levels reported in the literature for GaP. States are arranged from top to bottom chronologically, then by author. At the left is an indication of the method of sample growth or preparation liquid phase epitaxy (LPE), liquid encapsulated Czochralski (LEC), irradiated with 1-MeV electrons (1-MeV e), and vapor phase epitaxy (VPE). Next to this the experimental method is listed photoluminescence (PL), photoluminescence decay time (PLD), junction photocurrent (PCUR), photocapacitance (PCAP), transient capacitance (TCAP), thermally stimulated current (TSC), transient junction dark current (TC), deep level transient spectroscopy (DLTS), photoconductivity (PC), and optical absorption (OA).

We now discuss some of the experimental aspects of temperature spectroscopy. Lang (1974) called his original method deep level transient spectroscopy (DLTS), and he measured capacitance transients produced by voltage pulses in diodes made from conductive materials. However, in SI materials, this method is not feasible and an alternate method, involving current transients produced by light pulses in bulk material (or Schottky structures), was... 

A deeper insight into the lateral electrical homogeneity of the films, the limiting mechanisms of the Hall mobility, and the thermal activation energies of shallow and deep defect levels can be gained by temperature-dependent Hall and deep level transient spectroscopy (DLTS) measurements [57,59,60]. To give an example, the temperature dependence of the Hall mobility and... 

Capacitance transient spectroscopy encompasses a powerful set of techniques to detect and characterise deep levels in semiconductors. The list of techniques applied for III-V nitrides includes deep level transient spectroscopy (DLTS) [1,2], double correlation DLTS (DDLTS) [3], isothermal capacitance transient spectroscopy (ICTS) [2], photoemission capacitance transient spectroscopy (ODLTS) [4] and optical ICTS (OICTS) [5], This Datareview presents the current status of deep level studies by capacitance transient techniques for III-V nitrides. A brief introduction to the techniques is given, followed by an example that demonstrates the application of DLTS and DDLTS for Si-doped... 

Some of the metastable centers have been associated with impurities such as oxygen (Crandall, 1981) and carbon (Crandall et al., 1983). Deep-level transient spectroscopy (DLTS) has been used to identify a center associated with oxygen that has a characteristic activation energy of 1.0 eV, whereas... 

The first of these approaches is used in the technique of deep level transient spectroscopy (DLTS), which is perhaps the most common experiment for measuring deep levels in crystalline semiconductors (Lang 1974). The DLTS experiment is the measurement of the transient capacitance of a Schottky contact to the sample and is... 

Deep level transient spectroscopy (DLTS) measurements were carried out between 4 K and 300 K. We investigated single crystals grown by SCVT... 

Characterization of radiation-induced centers in the p -n-structures was carried out by means of deep level transient spectroscopy (DLTS) [3]. Concentrations, activation energies of charge carrier emission, and apparent capture cross sections of carriers were determined for all the traps observed. 

Optical techniques like photoluminescence (10) and infrared photothermal spectroscopy (11.) work well for the characterization of shallow level impurities, while electrical techniques work well for deep level impurities. There are a number of methods that have been used for electrical characterization. I will only discuss deep level transient spectroscopy (DLTS), however, because it has become the most popular and gives a fairly complete characterization. 

DBST (p,p -dibutylsexithiophene) 77, 80 ff DCNDBQT (a,cD-dicyano-p,p -dibutyl-quaterthiophene) 76 ff deep level transient spectroscopy (DLTS) 428, 437, 438 deep trap 437, 433, 441 deformation pattern 264, 276 degradation 373 ff., 393 ff, 553 demodulated reader signal 9 density functional theory (DFT) 264, 539 density of states (DOS) 428, 437 depth profile 404 ff., 436, 544 de-trapping 428, 437 ff, 441 device simulation 433, 435 dewetting, post-deposition 220 ff. DHBTP-SC ((dihexylbithiophene)2-phe-nyl swivel cruciform) 96 ff. 

The most widely used of these methods in the study of a-Si H have been field-effect, capacitance, and deep level transient spectroscopy (DLTS) measurements. Capacitance measurements actually include quite a number of variations such as capacitance versus applied voltage (C- V), frequency (C- w), or temperature (C-T), and also several kinds of distinct capacitance profiling techniques. The technique referred to as DLTS normally includes both capacitance-transient as well as current-transient measurements and will also be used as a generic term for such recent variations as isothermal capacitance transient spectroscopy (ICTS), constant capacitance methods, and the like. 

The development in 1974 of deep level transient spectroscopy (DLTS) by Lang and co-workers (Lang, 1974 Miller et ai, 1977 Lang, 1979) coupled the idea of the transient measurement method with the temperature scan-... 

It should be noted that a-Si H exhibits a density of states that is neither constant nor discrete. Deep-level transient spectroscopy (DLTS) (Lang et al, 1982), optical absorption (Jackson and Amer, 1982), and photoconductivity (Jackson et al, 1983b) measurements have indicated that a rather broad defect band lies in the gap and is centered below the Fermi energy. This means that for cases in which the built-in potential is less than the width of... 

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