Christoph Wolf

11 Questions 13 Answers 0 Followers

Questions related from Christoph Wolf

Does anyone know a source for LEDs with known emitter material and emission zone structure?

Dear all! I am trying to buy a set of reference light-sources (ideally Ga-In-N based MWQ) with known emitter material and known structure. Since both are more or less IP of the companies most...

02 November 2016 4,045 1 View

DFT: in bulk band-structure calculation is there a need for supercells?

Dear all! In DFT supercells are used to study surfaces by introducing artificial vacuum. But some publications use supercells even though they study (infinite periodic) bulk band-structures. Is...

05 July 2016 3,528 5 View

Is there a theory that supports a continuous temperature dependence of the exciton binding energy?

Dear Colleagues! Usually the exciton binding energy of a material is given in form of a number (~40 meV) but the temperature dependence is either not strong or not usually studied. In term of...

26 March 2016 9,332 2 View

Large Huang-Rhys parameters from temperature dependent absorption but very narrow PL emission - implications?

Dear colleagues! I have a question regarding the connection between absorption and emission of light in a poly-crystalline (solution processed inorganic) semiconductor. from absorption data I...

22 March 2016 6,354 3 View

What is the best instrumentation choice for measuring absorption of rough thin film samples?

Dear Colleagues! I am currently measuring the absorption of "absorbing thin films on non-absorbing substrate" type samples. The semiconductor material has a gap in the visible region and I am...

04 March 2016 3,061 6 View

What is the temperature dependence of the PL intensity in an indirect band-gap material?

Dear colleagues! In direct band-gap materials with increasing temperature the increasing probability of exciton dissociation decreases the PL intensity. In indirect band-gaps the increase in...

14 October 2015 6,987 2 View

How do I treat the transition between excitonic absorption and the Urbach tail?

Dear colleagues! I am wondering if there is any method to properly treat the transition from absorption by gap states (Urbach tail) to excitonic or band-to-band. When modelling all contributions...

30 September 2015 2,826 0 View

What is the best practice to hook up an oscilloscope to a biased device to monitor the transient signal?

I am currently trying to hook up my oscilloscope to a biased thin-film diode to measure the mobility in a TOF setup. However I am having a problem getting a good transient signal (for example for...

12 August 2015 2,650 5 View

How do I simulate Capacitance-Voltage (CV) characteristics of a Schottky contact using COMSOL?

Dear Colleagues, I am currently trying to validate some CV data. Therefore I would like to model the CV characteristics (capacitance at different bias levels) I am new to COMSOL but it is the only...

26 May 2015 7,480 2 View

CH3NH3PbBr3 first principles calculation - what is a good starting configuration?

Dear Colleagues! Recently I have been trying to calculate the electronic band structure of a organic-inorganic lead halide perovskite structure, namely CH3NH3PbBr3. I am not an expert in band...

18 April 2015 5,534 4 View

What is the easiest way of reading a 16x16 sensor prototype using a parameter analyzer?

Dear Colleagues, I am trying to readout (current or capacitance) of a 16x16 sensor prototype. I am wondering what is the easiest way of reading the matrix (I am using a parameter analyzer)? Does a...

15 March 2015 1,281 1 View