Danmin Chen

15 Questions 2 Answers 0 Followers

Questions related from Danmin Chen

Could you explain in layman's term how quantum tunneling in superlattice is related to semiconductor performance?

As I read superlattice is a type of heterostructure with quantum tunneling.

18 February 2022 355 0 View

Flux transient with heat loss when source shutter opens during MBE growth?

How is it that reducing charge volume in crucible can help minimize heat loss, thus leading to more stable flux?

21 January 2022 5,270 1 View

When growing DGSL(digital graded Superlattice), how to ensure sufficient ramp rate for the decreasing temperature?

For instance we decrease temperature of Al effusion cell while increase In temperature. What if the ramp down rate of Al cell is not as fast as needed to ensure correct composition?

10 January 2022 7,787 0 View

Rheed or LLS to study MBE surface morphology?

For in situ monitoring of surface degradation or reconstruction during sample growth in MBE, what are the differences between RHEED and Laser Light Scattering?

10 January 2022 711 0 View

Why is a molybdenum blank preferrably loaded onto sample manipulator during MBE baking out?

The bake out temperature is low 200℃ and manipulator has PBN heater that can tolerate high temperature；molybdenum has poor thermal conductivity

10 January 2022 3,895 2 View

Why is Hall measurement for carrier concentration performed under vacuum?

A vacuum condition with lower than 50Pa is required. Plus, what are the conditions people consider whether ECV or Hall is chosen for carrier mobility/concentration measurement

08 January 2022 5,802 3 View

For MBE operation wafer transfer before or after heating via manipulator?

Let's say optimal temperature is set at 600 degree Celsius. Is the wafer transferred onto the manipulator holder and heated from RT to 600, or the manipulator has been ramped up to 600 and kept...

11 December 2021 7,432 5 View

In MBE growth how do arsenic dimer or phosphorus dimer fit onto substrate lattice?

Arsenic or phosphorus leave the cracker as dimer; does the covalent bond break before the individual atoms fit onto substrate surface?

08 December 2021 6,098 1 View

How do MBE source As cracker and P cracker control BEP?

Is it fair to say that As or P sources BEP are controlled by the needle valve position rather than temperature control (as opposed to other standard effusion cells like Ga, In, Si etc)? The...

19 November 2021 8,526 3 View

MBE Molecular Beam Epitaxy pretreatment chamber?

Why a separate pretreatment chamber is designed when the linear buffer chamber already has filaments for wafer degassing? What are the differences between these two chambers in terms of their purpose?

15 November 2021 213 3 View

Can you recommend an IR thermometer with spectral response below 2000nm?

IR thermometer used for high temperature measurement (around 1000 degree Celsius) through quartz glass

02 November 2021 6,032 5 View

Why CdTe buffer layer is needed as a transition to HgCdTe when using Si or GaAs substrates?

Any different buffer layers possible?

30 October 2021 446 7 View

Flux calibration for molecular beam epitaxy?

What are the general methods to calibrate atom fluxes with MBE? How do you relate effusion cell temperature to flux pressure in Torr?

22 October 2021 8,379 3 View

Aluminium effusion cell requires a cold-lip heating mechanism?

The lip is kept at a lower temperature due to wetting of PBN. Can you explain why Al overflows

12 October 2021 7,898 2 View

Possible modifications for PBN heater to achieve better cooling ramp rate?

We use PBN graphite heaters for effusion cells but the cooling rate is not as desired. What are the possible modifications that can be done to the heater to achieve more swift cooling?

01 January 1970 3,036 2 View