Semiconductor Devices

In this laboratory exercise you will examine semiconductor devices such as signal diodes, light emitting diodes, Zener diodes, laser diodes, solar cells, MOSFETs, JFETs, or bipolar transistors. We will measure the electrical charateristics of the devices and also look at the temperature dependence of the electrical characteristics. From these measurements we will try to extract some semiconductor properties like the band gap or the doping concentrations. If possible, we will look at the devices in an electron microscope. The reports will be written using the FAIR Principles of data management. FAIR stands for Findability, Accessibility, Interoperability, and Reuse of digital assets. Your measurements will be described in a way so that someone else could reproduce them and you will make the raw data available for others to analyze.

This is an example of a measurement script that reports measured data to ELab

that needs this library eLabFTW_config_api2_semilab.py to be modified as described here

from KeithleyV15 import SMU26xx
import matplotlib.pyplot as plt
import time
import datetime
import csv
import numpy as np

#for use of ELABFTW
import os
import elabapi_python
import eLabFTW_config_api2_semilab as eLab
import json

"""
EXAMPLE: characteristic curve of a diode

Schematic:

--------------
    |            |
  -----         -|-
  | A | SMU     \|/
  -----         -|-
    |            |
    --------------

"""

""" ******* Connect to the Sourcemeter ******** """

# initialize the Sourcemeter and connect to it
# you may need to change the IP address depending on which sourcemeter you are using
sm = SMU26xx("TCPIP0::129.27.158.188::inst0::INSTR")

# get one channel of the Sourcemeter (we only need one for this measurement)
smu = sm.get_channel(sm.CHANNEL_A)

""" ******* Configure the SMU Channel A ******** """
#define a variable "current range" to be able to change it quickly for future measurements

current_range = 1e-8
current_range_for_name = str(current_range)

# reset to default settings
smu.reset()
# setup the operation mode of the source meter to act as a voltage source - the SMU generates a voltage and measures tcurrent
smu.set_mode_voltage_source()
# set the voltage and current parameters
smu.set_voltage_range(20)
smu.set_voltage_limit(20)
smu.set_voltage(0)
smu.set_current_range(current_range)
smu.set_current_limit(current_range)
smu.set_current(0)

""" ******* For saving the data ******** """

#some suggestions for improvement of the data saving
    #the file name should identify the file uniquely
    #therefore specifying for example the voltage range, and the
    #type of characteristic (U/I, U/R, etc...) is suggested

# Create unique filenames for saving the data
time_for_name = datetime.datetime.now().strftime("%Y_%m_%d_%H%M%S")
filename_csv = 'Diode_' + 'current_range_' + current_range_for_name + '_' + time_for_name +'.csv'
filename_pdf = 'Diode_' + 'current_range_' + current_range_for_name + '_' + time_for_name +'.pdf'

# define the title of your experiment, under this name the experiment will be stored in ElabFTW
exp_title = "Red Diode Measurements"

#initializing a CSV file, to which the measurement data will be written - if this script is used to measure anothcharacteristic than the U/I curve, this has to be changed
# Header for csv
with open(filename_csv, 'a') as csvfile:
        writer = csv.writer(csvfile, delimiter=';',  lineterminator='\n')
        writer.writerow(["Voltage / V", "Current / A"])

""" ******* Make a voltage-sweep and do some measurements ******** """

#some suggestions for the improvement of the measurement process
    #it would be nice to have a primary measurement, in which the
    #type of junction was be determined and a parameter was set
    #that indicated the forward direction of the junction
    #this primary measurement could also be executed and inlcuded
    #in the file name
    #this procedure would spare us the time of finding the forward
    #direction

# define sweep parameters
sweep_start = -2.50
sweep_end = 2.5
sweep_step = 0.01
steps = int((sweep_end - sweep_start) / sweep_step)

# define variables we store the measurement in
# rename if needed
data_current = []
data_voltage = []

# enable the output
smu.enable_output()

# step through the voltages and get the values from the device
for nr in range(steps):
    # calculate the new voltage we want to set
    voltage_to_set = sweep_start + (sweep_step * nr)
    # set the new voltage to the SMU
    smu.set_voltage(voltage_to_set)
    # get current and voltage from the SMU and append it to the list so we can plot it later
    [current, voltage] = smu.measure_current_and_voltage()
    data_voltage.append(voltage)
    data_current.append(current)
    print(str(voltage)+' V; '+str(current)+' A')
    # Write the data in a csv
    with open(filename_csv, 'a') as csvfile:
        writer = csv.writer(csvfile, delimiter=';',  lineterminator='\n')
        writer.writerow([voltage, current])

# disable the output
smu.disable_output()

# properly disconnect from the device
sm.disconnect()

""" ******* Plot the Data we obtained ******** """

#use plt instead of semilogy to plot in chartesian axis
plt.semilogy(data_voltage, np.abs(data_current),'x-', linewidth=2)

# set labels and a title
#suggestion: include some more information about the measurement (ref CSV file title)
plt.xlabel('Voltage / V', fontsize=14)
plt.ylabel('Current / A', fontsize=14)
plt.title('Characteristic curve of a diode', fontsize=14)
plt.tick_params(labelsize = 14)

plt.savefig(filename_pdf)

# Connect to eLab

elab_manager = eLab.Helper_elabftw()
experiment_ID = elab_manager.set_experiment(exp_title)
print(experiment_ID)

# Upload files to eLab
filename_scr = __file__
elab_manager.upload_file(experiment_ID, filename_csv)
elab_manager.upload_file(experiment_ID, filename_pdf)
elab_manager.upload_file(experiment_ID, filename_scr)

#show plot

import os
import time
import datetime
import elabapi_python
from elabapi_python.rest import ApiException

""" **************************************************
    inspired by
    https://alexgu2008.github.io/elabftw_api_support/

for further documentation:
    https://doc.elabftw.net/api/elabapi-html/
    for further examples:
    https://github.com/elabftw/elabapi-python
    
    author: K. Zojer (April 2024)
""" **************************************************
#########################
#         CONFIG        #
#########################
API_HOST_URL = 'https://elabftw.tugraz.at/api/v2'
# replace with your api key
# for LabCourse Semiconductors
API_KEY = ' ---ENTER-YOUR-APIKEY-HERE----'
USER_LAST_NAME = '---ENTER-YOUR-USER-LASTNAME-HERE----'
#########################
#      END CONFIG       #
#########################

class Helper_elabftw:

def get_myuserId(self):
        
        usersApi = elabapi_python.UsersApi(self.api_client)
    
        uresponse = usersApi.read_users()
    
        target_user_lastname = USER_LAST_NAME
    
        for user in uresponse:
            
            if user.lastname == target_user_lastname:
                #print("User ID of ", user.lastname," ", user.firstname, ": ", user.userid)
                self.userid = user.userid    
           
        return self.userid  
      
    def __init__(self):
        # Configure the api client
        self.configuration = elabapi_python.Configuration()
        self.configuration.api_key['api_key'] = API_KEY
        self.configuration.api_key_prefix['api_key'] = 'Authorization'
        self.configuration.host = API_HOST_URL
        self.configuration.debug = False
        self.configuration.verify_ssl = True
        # create an instance of the API class
        self.api_client = elabapi_python.ApiClient(self.configuration)
        # fix issue with Authorization header not being properly set by the generated lib
        self.api_client.set_default_header(header_name='Authorization', header_value=API_KEY)
        print(" user id:  ", self.get_myuserId())

"""==================================================================================== 
        provides the experiment_ID for the experiment matching the experimental title

input:
            experiment_title ... title of the experiment (type: string)
    """
    def get_existing_experiment(self, exp_title):

# default response if experiment is not found:
        experiment_ID = -1
        experimentsApi = elabapi_python.ExperimentsApi(self.api_client)

response = experimentsApi.read_experiments(owner=self.userid) 
        for exp in response:
        
            if exp.title == exp_title:
                print("Experiment ID: ", exp.id, " ", exp_title)
                experiment_ID = exp.id
                #print(type(response[0]))
            else: 
                print("Experiment does not exist yet.")
        return experiment_ID

"""==================================================================================== 
        provides the experiment_ID for newly generated experiment with given title and current date

input:
            experiment_title ... title of the experiment (type: string)
    """

def create_experiment(self, exp_title):

experimentsApi = elabapi_python.ExperimentsApi(self.api_client)
        current_date = datetime.date.today()
        response_body, status_code, response_headers = experimentsApi.post_experiment_with_http_info(body={'title': exp_title'date': current_date, 'tags': ['#semilab', '#SS2024']})
        #print(response_body)
        #print(status_code)
        #print(response_headers)
        experiment_ID = response_headers["Location"].split("/")[-1]
        response = experimentsApi.patch_experiment(experiment_ID, body={'title': exp_title})
        return experiment_ID
        
    """==================================================================================== 
    provides the experiment_ID for the experiment matching the experimental title

input:
        experiment_title ... title of the experiment (type: string)
    """
    def set_experiment(self, experiment_title):

experimentsApi = elabapi_python.ExperimentsApi(self.api_client)
        experiment_ID = self.get_existing_experiment(experiment_title)

if experiment_ID == -1:
            print(" Create experiment: ", experiment_title)
            experiment_ID = self.create_experiment(experiment_title)
        
        return experiment_ID

""" 
        uploades a file to the experiment specified by experiment_ID

input:
            experiment_ID   ... ID of experiment
            filename        ... name of the file to be uploaded
                                merge path with filename if file is not in the local directory
    """
    def upload_file(self,experiment_ID, filename):
        
        uploadsApi = elabapi_python.UploadsApi(self.api_client)
        #local_file_path = #r".\\ "  
        
        #try: 
            #uploadsApi.post_upload('experiments', experiment_ID, file=local_file_path+filename, comment='Uploaded with APIv2')
        uploadsApi.post_upload('experiments', experiment_ID, file=filename, comment='Uploaded with APIv2')
        #except ApiException as e:
        #    print("Exception when calling UploadsApi->postUpload: %s\n" % e)
        return







Semiconductor Laboratory